Just did some inspection on my upper. There is pitting on some of the gears but not all. Is it a tough change or no? I've pretty much done all my own work on my boats for years, but I've never had a drive apart. Any ideas?

Haven't ever done a XR but the standard Bravo is not hard so long as you have the special tools and the manual. It does take several special tools, cost me almost a grand by the time I was done rebuilding the B3 lower

Its not hard, but you will have at least $1000 in tools to do the upper, and then another $1600 in gears. It would be cheaper to just take it somewhere and have it done.

You need the wrench the get the pinion retainer nut off, if you have the puller to remove the tower races and the clutch shaft bearings and the driver to set the height of those, that's one step, you need an inch pound torque wrench to set the rolling resistance of the pinion bearings, the tool to check pinion depth, and the couple of tools needed to check the backlash, need to have a variety of sizes of the thrust races and the pinion shims and the patience to check and adjust if needed