Should be fairly easy except for the wiring for the computer controls and the automatic overdrive transmission. If the wiring doesn't scare you,none of the mechanical work will. The 55's came stock with the Y-Block V-8's,and everybody on the planet was swapping big block FE engines into them in the 60's using all Ford parts.
If you have never done this sort of thing before the best advise I can give you is to find somebody who has done engine swaps before,and get them to help you. Chances are you don't even have a cherry picker or the other tools needed to complete the swap,and they will.