Regarding weight, the 2 rotor shortblock in my FD weighs around 200 lbs. I lifted a spare motor into the trunk of my Mini once to get it home.
The 3 rotor is a little heavier than the 2 rotor, obviously. A good estimate using the 2 rotor as a baseline might be around 300 lbs.
Check out what this shop does with a N/A 3 rotor conversion for the FD chassis: http://definedautoworks.com/ They have some nice You Tube vids also.
