I rebuilt my Dana 80 axle in February of 2013. It was the first axle I had ever re-geared / rebuilt. I did not have a bearing preload measurement tool. It took me nine days from start to finish with 30 hours of actual work. The abbreviated timeline was: make special tools, buy socket to fit pinion nut, tear down, order parts, clean, measure components, parts arrive, re-clean, assemble, measure, tweak shims, measure, tweak shims, check contact pattern, when pass install new seal, install yoke, install new nut and washer, install cover, add oil, reattach drive shaft, burn rubber.
I bet I put the pinion and case in and out at least 6 times each before I was satisfied with the fit. I must have got it right though because I pulled a 12,000 pound trailer on a 3000 mile round trip 4 weeks later and the case temp never got above 175 degrees F. I have not had any problems with the axle to date.
I rebuilt a Dana 60 axle for my neighbor in March 2013 and it only took me 10 hours of actual work. Most of the time savings was due to having special tools already made. He has not reported any problems with his axle yet.
If you choose to re-gear the axle yourself I will offer the following advice.
1. Use Dana gears if you plan to keep the truck for a long time. I used Yukon gears in the first axle I rebuilt. The surface texture left something to be desired, and the pinion gear run-out was barely within tolerance. Tooth to tooth backlash variation was as high as .002" and the target .005"-.008" factory specified backlash value was a bit out of reach. I ended up settling for .004"-.009" range, and that is with a case that had no significant run-out.
For the Dana 60 axle I rebuilt I used Dana gears, and there was a big difference. The surface texture was very smooth and run-out was very low. Tooth to tooth variation in backlash was less than .001" and the variation of .005"-.007" backlash was well within the ford specification. I suspect that the majority of this variation was actually coming from the case itself and not the gears based on the .001" run-out that was recorded during pre assembly measurement.
2. Make sure you have an impact wrench that can deliver 1,200 ft-lb of nut busting torque to get that pinion nut off or you could find yourself with some tired arms. Also avoid using a pipe wrench to hold the pinion yoke unless you plan on buying a new one. I recommend building or buying a tool with flat faces to hold the yoke while that impact wrench is getting things done for you.
3. That preload measurement tool can save you a lot of time if you can get one from somewhere. I've never used one, but after the nth time of in and out with the pinion to get the shims added between bearings I was definitely wishing I had one.
4. A bumper jack or equivalent system is great at allowing the axle to hang fully suspended. This is a must if you have a rear fuel tank.
5. Have an extra pinion seal on hand just in case the first one doesn't get in straight on your first attempt.
That got long fast. If you would like more info/advice feel free to ask. If not there's always the "other guys on the internet"