In the early 80s there were a couple years that ran a vacuum disconnect front axles (2 axles shafts with a locking collar). You can tell if you've got one by the big vacuum motor on the diff (or lack of). That won't make any difference in u-joints though...and honestly they shouldn't even be asking you with your '77.
That aside, to do the u-joints you have to take off the wheel, hub, and spindle. It's not REAL hard to do, but plan on it taking a little while. When I did mine the 25 year old u-joints had become very comfortable in the axles shafts. lol It took some persuasion and a ball-joint press to get them out.
1983 J-10 - 4.6L(MPFI)/CS144/NV3550/D300/44/44/3.54/32
1983 Honda CB1100F
1983 Honda CB1000C