Re: good bye j-body hello g-body 
i haven't done it yet and thankfully ill just be dropping a motor in with new headers but from what iv heard its a b*tch and its possible to finagle them in there, and a few people have said its easier from the bottom if you have a lift or i suppose you could jack it up high enough.... nice ride and welcome...
as far as your questions, brake lines: you should check where all chevys rot either ontop of the dif or follow them along the frame rail, generally the driver side goes more often than not... i havent checked my self but i think the gbody is the crossover brake line design where the lines make an x somewhere near the transmission and go back to the respective caliper but dont quote me on that v.v..... also if you broke a stud off in the manifold..../sadface get as many out as you can and pull the manifold off, then youll need to find a torch and see if you can get the stud out.... heat, cold water and then turn with a stud puller socket its a pain in the *ss and honestly rusted studs is really the only downside of liking old sh*t v.v
but good luck and nice buy, especially compared to what you were driving lol
