Mate you have asked the right questions, i own a garage and also prep rally cars and build them. To do a rebuild yourself would be a bit of a risk without the right tools. also you need to know your ring end gaps and what measurements you have in the big and little ends for play and horn out the block if needed. Myself I like to get a builder to carry out a 'freshen up'. I would go new rings (if within limits) new shells and skim, gaskets etc but they will talk you through all that and a price mate hope that is some help