Out of curiosity, when you say "Large Screen" is it a 15" or a 17" model?
In either case unfortunately it sounds to me like "find a less dinged one" might be the best solution. Without seeing the damage directly I probably can't do much more than guess at what you could do to relieve some of the worst of the problems, but... broadly speaking construction-wise the Aluminum Powerbooks are basically a metal tray (the lower case) in which all the guts are installed and covered by a cap (the upper case sheet in which the keyboard rests inside a recessed pocket) with the display assembly cantilevered out into its notch with a hinge on either end. The problem with the design is the bottom case is basically one big stamping, sort of like a cookie sheet, and if you've ever dealt with a warped cookie sheet you'll know how once you manage to put a twist into them it's well neigh impossible to make it straight again. For dents you can remove the innards and hammer the dents back out (although if it's a corner it's probably not going to go well; I tried to massage a dented corner out of a 15" one once and I think I just made it look worse because the aluminum looked cracked once the dent was reversed; pulling a dent out of a long edge is more successful) but a major bend that makes it look cockeyed you're probably stuck with. (By "palm rest separating" do you mean the metal has pulled away from the plastic frame around it? That's probably evidence that your bottom case is indeed bent and is putting torque on the case cover. As you can see here the top case is a composite structure that under some circumstances is more likely to pull apart than bend.) Dents in the LCD cover are another kettle of fish. The LCD housing is a combination of snapped and glued together so unless the dent is so bad as to actually be structural (which I'm not sure is possible without breaking the LCD, although the glass is flexible enough that if the whole Powerbook were bent slightly it might hold together) you're better off leaving that alone. I know there are *some* people that can pull those apart in their sleep but I did it once and it was horrible.
If you wanted to post a few pictures of it there's probably a few people who watch these forums more skilled than I who could give you some concrete advise about how to resolve the problems that are actually operation-affecting.