Are you threading that bolt in from the back?
My engine is built and on the airplane - don't think I want to be hammering on anything
I’ve done this a number of times using a bolt, washers, nut, and large socket, and never had to tap on anything with a hammer - just use the force generated by turning the nut on the bolt. Note that I am not using the drive lug bolt is small enough diameter to go straight through.
Then reverse the process from the front side to press in the new lug?
Yes - you just pull it into position.
Then reverse the process from the front side to press in the new lug?