ya ebay is a really big crapshoot like duster_360 said. i have bought dozens of parts off ebay for my savage 25 some are used and some are new from hobby shops.

for the sticky throttle.. pull off your carb and pull it apart,like all the jets and stuff and clean it with some kind of solvent and blow the crap out of it with air and make sure it is dry inside. then put everything back together and set the jets back to factory (flush with the housing) and go from there. pull the return spring off too and move it by hand, then do the above as i mentioned, and it should work. also make sure the linkage is not binding or catching on anything. if not i'd probably just replace the guts in the carb. it sounds like a carb problem to me.