5th gear damage am going to change the gear ,but have heard that you can change the gear so that there is not a big change from 4 to 5th, can anyone tell me what size to look for. and were to get gear parts.

Try here for a step by step description of how to do the job yourself -
https://docs.google.com/document/d/1TSJWOFLsFsz_oqRra9nFKDrVjYG6Y0Zxvlizd6rq8bg/edit?pli=1 there was a link to the pictures on photobucket that Garry put up to correspond to his guide, as well as link of the step to step pictures on the Fiat forum somewhere which I posted as well but I think they have been deleted by now.
& here is a place to access the parts for the lower ratio 5th gear- http://www.essanjay.co.uk/services/
see bottom of the page.
Cheers