Use lots of PB Blaster on the frozen nuts and bolts. Get it at walie mart or parts house. Just keep spraying it everyday. the stuff on the label is true. This may be a silly question but here goes. If engine, trans and diff are all good why take them apart? Just keep everything pluged so sand and dust stay out. Drive train parts are easy to remove if they fail and you have less to put back in your jigsaw puzzle.

There is no mechanical problem so difficult that it can not be overcome by brute force and ignorance.