I hadn't heard of VET until today. As the Sibelius template developer here at TWS, I have no plans at the moment to produce one for VET. Does the library include a .sib and/or sound set at all?
As far as doing things yourself, I don't know of a good resource outside of the Sibelius User Guide - other than just digging in and figuring out how stuff works. Two quick tips I can give you here are, 1) make sure the sound set is fixed up properly before mapping the instruments, 2) make a layout of the proposed mapping before starting to assign sound IDs (Program Names) to mapped notes.
As far as doing things yourself, I don't know of a good resource outside of the Sibelius User Guide - other than just digging in and figuring out how stuff works. Two quick tips I can give you here are, 1) make sure the sound set is fixed up properly before mapping the instruments, 2) make a layout of the proposed mapping before starting to assign sound IDs (Program Names) to mapped notes.