looking for a 3400...

Now, i know its possible to switch from a 3100 to a 3400. My question is, how big of a project am i looking at? Will it drop in if i get the same year engine? My car is a Olds Cutless Ciera '94 (3100 V6) and the intake gasket is falling apart (the exhaust is sweet and has a white smoke when it gets warm). HOwever, is it possible to take my 3100 tear it down and put the top end of a 3400 on it? Then, if i did that, would it be possible to s/c it? Or is it easier to drop the 3400 in? Any help is great!!!! :D