yeah the tensioner pulley will do the sound.. not sure which one on your truck. open the hoood with the truck running and listen and feel for vibration (of course whatch tyour little fingers!)
that's a great deal man... if r50 is anything like wd21 that's a steal, really.
i'd say if you get 1k that'd prob be good.. should be enough time to find out if anything is up although your trip south will eat all that up so bargain with them... i think 3k-3mo is about the standard in the industry (chain shops)