Hey, you gotta know your limits!
My husband and I bought an older house back in '93. We stripped the wallpaper in the bathroom and hubby tried to re-plaster the walls. It cost an awful lot, when the plaster guy came, for him to take down hubby's stuff first.
However, when the hot water heater broke, hubby ran down to Home Depot and picked one up, and he and his brother installed the new one in a couple hours. That saved us plenty.
Follow your talents!
Sheetrock, on the other hand, can be managed by anyone with a modicum of patience and attention to detail.
My husband and I put down parquet floor, installed wiring, and sheetrocked the walls and ceiling of the baby's room when I was nine months pregnant. I can still mud, sponge, and sand a seam so that you can't tell it's there (the sponge at the exact level of dampness is the secret trick.)
It doesn't insulate sound the way plaster does, but since 2 of the 3 walls were furring strips on concrete block, it didn't matter (we put sound damping insulation in the 3rd wall on the bathroom side.)
We're very gung-ho DIYSers -- have to be, it's too expensive to hire contractors to do every little thing, and I do a better job on fiddly detail work. (We did hire a man to paint the house, he was very reasonable and quick. He had a crew with pressure sprayers -- we don't.)