As for your original question, you can do this yourself. I've done it
some time ago. Your job will be made easier not having an air
conditioner to contend with.

Just get the right belts (you can assume yours are stock for your year
car if nothing's been modified) and take off the front one to get to
the back one. Have an appropriate stick to use as a lever--and a friend
if you can round one up--to help retension the belts. A hammer handle
works for me. Don't get them too tight or too loose. Pay attention to
the bentley manual and to the tension of the belts before they come
off, at least you can use that as a "not looser than" guide when the
new ones go on.

Tensioning belts is something the shop can POTENTIALLY do better than
you, but I've never had it done by a shop in my life. You can always
retension if they slip or squeal, just don't tighten too much.

Jim