how hard is it 2 do on a 84 f-250 4x4?

Get a Chiltons. I have replaced and rebuilt FWD CV joints which aren't that difficult. The main thing is to get step-by step instructions, read through them before loosening a single bolt, and make sure you have the proper equipment. I know this doesn't answer your question directly, but I have never worked on a axle joints on a 4X4, so I cant give you a straight answer. I am confident in your abilities so long as you have a good manual, all the necessary tools, an extra set of hands, and have turned a wrench at least once before.

Good luck and let us know how it goes.

got um done in bout 5hrs not bad considering all the rust

Glad to here it!