I have an Oliver Super 66 with an aftermarket 3P.H. and it sure is nice. It was on the tractor when I got it so I can't say how difficult it is to put on...... and yes it is harder to get up on the tractor, but I don't have the steps so I lower the 3 P.H. about half way or so and that acts as my step. (My Super77 has just the rigid hitch which also serves as my step)
     If you have much occasion to use the 3 point hitch, then you will like it on your 77 and I think you can also keep the step on your tractor....don't take my word on that, better make sure on that one!
                       Cal