I wholly agree with the idea of doing as much yourself as you can, for much the same reason, learning something new.
I had a fair bit of worry over our setting out, despite having checked and double checked that the critical stuff was in the right place. Just as well I was so concerned about getting things in the right place, as we ended up with a foul drain stack coming up closer to the inside edge of a wall than I really wanted. My fault for thinking that having it within ~±30mm would be OK, it really needed to be within about ±10mm of where it needed to be.