96 monte carlo engine replacement

I am looking to replace my current 3.4l dohc engine in my 96 z34, as it seems to be shitting the bed and has 125,000 on it. have seen any new 3.4 crate engines sold by chevy and was wondering how much trouble it would be to put in a 3.8 3800 Supercharged V-6 Crate Engine or appox. cost to have it installed. any help will be greatly appeciated, THANKS!

Subframe, pcm and harness, all the matching sensors, trans has different bell housing, just some issues. Better off looking for a 98-99 Monte Ls with the 3800 11.