I recently dumped it in reverse by accident and s***t happens, the gear crunches and engages for abit then pops back out, I'm thinking of rebuilding that gear and I'm not sure where to start from, plus I have a mate who's got a t5 but the synchros are gone so 3rd and 4 the doesn't work, is it easier to rebuild or change the synchros on the other box, if so what price range am I looking at if I took it to get a rebuild or doing it myself, please help guys I'm new to t5s and how they behave

Hi just wondering if changing the reverse gear in a t5 box is easy, if so does anyone have any tips for it?

Get a good workshop manual and study it ( manual gearbox rebuild).....then decide if YOU have the tooling and talent/knowhow to do it.
Not takin the p!ss, just letting you decide.