DIY vs Have it installed

I think the brand name on mine is "silestone" or something like that. I've actually seen natural stone sinks, and while they looked cool; they are not for me. stone is absolutely unforgiving, and I am not that careful. I can plunk a plate down in my sink; and it won't break the plate.

other than the main pipe to the septic tank, the plastic pipes I replaced the original drains with were as large or larger than the original pipes - BEFORE they were narrowed by sediment and rust scale. our toilets drain through 3 inch ID pipe.

I like this idea. But, still waiting for natural gas to make it to my house. For some reason, it stopped 250 feet down the street from me...

The one we have here is stainless steel, (Its a double) three hours to put in place, part of that was putting plasters on finger cuts.

This is how it sort of went in my house, when we replaced two circular sinks that were not big enough to was a single cup in with one BIG double sink you could wash a dog in.....

Whatever you buy, if your going to need to cut a new hole.
Place the new one upside down over the old hole in the right place, and draw round it.
Then take a look under the top you just drew on and work out if you have enough space to make that cut without moving things about, like supporting walls, cupboard walls, whole units, etc....
When you have the sink in the right place, draw round, then remove the sink, draw another line about an inch inside that one, that will be your cut mark....
I would suggest a Router to cut the hole, it makes a nice even cut in most surfaces, from any kind of wood to composite plastic surfaces, but ALWAYS check below the surface to see what else you are cutting through.....

Also think Pipework.
Twin sinks usually join in pipework underneath.... have you got cupboard space to do that under the sinks, do you need to cut through cupboard walls to do that, or have you got space to join the pipework behind the sink units....
If I did ours again, I would send both waste pipes out through separate holes in the wall on their own without trying to join them under the sink.... the headache I had trying to get a set of drain pipework that fitted was a complete shambles, and what I have is self-made, as it works better, and doesnt leek all over the place like the one they sent with the sink did....
And trust me, cutting a second drain hole in the wall with a JCB (Back-Hoe is USA) would have been a lot easier than the two months I spent trying to get the pipework they sent with the sink working.....
It never worked properly.

Flexible hose pipes about a foot long or longer, for hot and cold, are worth their weight in gold..... but dont get the ones with isolator valves on them, the valves need to be separate.
You can affix these to the sinks taps whilst the sink is out on the bench, which is always easier, then do the final fix where you can see the joint below the sink level.
Its also better to be able to remove those whole flexible pipes and sink if you ever change taps as well...
This way you aint trying to hold the tap still with one hand whilst you get some form of spanner twisted up behind the sink where you cant quite see it properly with the other and find out your arms are not that long anyway.........
Whilst you have the water off, if you havnt already, put an isolator valve on those water pipes below the flexible hose...
Those hoses are pretty much bomb-proof anyway, but you never know......

Send the wife out for the full day.
Give her the credit card even....
You know it makes so much sense...
You KNOW she will find every opportunity to find something that needs water, just so she can remind you how long you are taking, and how much she needs that sink....
Maxing out the credit card takes less stress to fix that telling the other half you are not finished yet every five mins and no she cant use the water yet...

No problem, those things are flexible. But I had missed how they managed to do spots where the pipes branch out.

The floor is still fully intact, it still has the special paint on top I used to stop the smell as a temporary fix. There is only one spot they had to open and that was a drain with a one way valve they had to replace in order to connect it to the new pipe. I have no idea how they made the connections! They have cut off all vertical pipe which came out of the floor but most joints were inside the floor!

So it's faster?

Nothing is as simple as it seems...

I learned that I couldn't just get a 3/8" coarse -> 3/8" fine adapter (at least not at Home Despot)

So, on the plumbing guys suggestion, I tried a 3/8" compression -> 3/8" fine after cutting off the existing pipe fitting

But, the pipe is NOT 3/8" OD, it is 5/8" OD...

Back to Home Despot for a 5/8" compression -> 3/8" fine, which it turns out is almost extinct as most modern plumbing is done in 1/4" increments, not 1/8" increments...

In the end, the 5/8" compression -> 3/8" fine did the trick.

(Added bonus: I now have a new pipe cutter and adjustable wrench...)

I'm just the opposite. Electrical and plumbing I'll do. The stuff I want to work right, I want to do. The stuff I want to look good, I'll pay the pros to do.

The good thing about remodeling is that ANYTHING you can do yourself will save you big money.