Ok so I have 2 questions really.



First, can arfcom recommend me a good interior door manufacturer?  I would prefer a solid core door mainly because I want to cut down on sound transmission as much as possible in the house.



Second, I've never replaced interior doors before.  Assuming the framing, dimensions and everything is fine, can I just unhinge the old and slap the new one on?  There are a couple of doors where the framing is in bad shape so I think I'd rather have a pro do those.  

When you say framing, are you talking about the door jamb, or the actual studs and headers? I'm assuming the door jambs, but I do have to ask.

You can buy just the slabs and hang them on the existing hinges. You can trim solid core doors on the top and bottom to make them fit, if needed. Hollow core doors can't be trimmed much because it's typically a thin piece of wood on the ends and hollow, or honeycomb cardboard, inside.

Replacing the entire jamb assembly isn't that hard. Just make sure to measure it right. Put the new pre-hung in and level, plumb, and square it, and you're good to go.