The input seal is inside the bearing retainer and the output seal should probably be replaced to be safe. If it was a good transmission 10 years ago and has had oil in it it should still be good.
Yeah, I once decided to tear a 435 down to see if it was good even though I knew it worked fine. Lifting it onto the bench murphy's law kicked in and the tranny slipped off almost landing on my feet and cracked the case. I fealt pretty smart right then.
Thinking about it I've dropped a couple transmissions. Dropped a friends NV4500/205 combo, actually, sort of caught it, but I'm not big enough to catch 400 pounds, I just slowed it down alot and screwed up my back.