Welcome aboard Cody.
Did the mechanic replace your drive because it was stolen while they had it, or did they locate a drive for you after it was stolen somewhere else?
I don't know the mechanical shifts well enough to answer your shift question. But you're sure they replaced the drive with the same drive and exact same shift? '78 would be a hydro-mechanical shift, '77 would have been an electric shift (totally different) and by '80 (I think) you'd be in a true mechanical shift.
Also, the steering on a Stringer drive is one of two types (again, I think): Tru-Course and through-the-transom push rod type. If it's Tru-Course, there's kinda' only one way to connect that up, so if it's backwards they've done the install wrong. Did you replace the helm and cable too, or just the drive?