I'd check to make sure the motors not rusted before buying a pullstart and airfilter for it.
Cause if its rusted its not worth fixing seeing a Brand new T-15 generally costs around $65 with pull start and airfilter included.

Stock servos are labeled either HPI SX-1 or HPI SF-1's personally I'd keep the jr high torque as the steering if its working

I got my savage like that with a friggin tank of fuel in it the engine was rusted. I swear how hard is it to drain the damn tank before you send it. Guy sounds like he wasn't that bright so you might be needing a new motor seeing thats how he treated the truck.

Personally I'd strip the paint off with paint remover or just buy a new bottom plate for $20. But I'm pretty anal about those kind of things.

Take a pic of it lets see what kind of shape its in