My party recruited a techpriest, and so far i've just been winging it with his abilities kinda using the explorator as a basis, but I want to flesh out his abilities more accurately. Does anyone have a techpriest profile, or at least some ideas about how I should go about making one? Should I just use the explorator?

Depends how good a techpriest he is and if he has any specialities.a rank 1 explorator is fine for a rank and file techpriest, maybe buff the intelligence and add some more cybernetics.

Yes, an Explorator is essentially a techpriest. Your other option is to generate a rank 5 or 6 techpriest from Dark Heresy.