The high rate of shop labor cost makes these things a replacement item.----But if you have the tools and search for repair kits it can be done I think.
I have done this job too many times. I don't think shop labor rate is why Volvo decided to only sell the complete assembly. Based on what I learned at Volvo drive school and doing the job.
Volvo is very proud of how quiet their drives are compared to MCM. What they said they were finding in the field was under trained techs didn't mark the yokes and reinstall them properly phased. Volvo claims to balance these assemblies and feels that maintaining that balance during u-joint replacement is almost impossible.
And to be honest, I probably did over 100 u-joints before hearing about this in school, ahh "the learning never ends. Guess who marked the yokes on the next few hundred jobs I did, did it for MerCruiser to because like the instructor said "can't believe we have to teach common sense".
From my own experience, Volvo yokes are thinner and pretty easy to bend, especially if the proper tools / techniques aren't used and/or there is rust involved. So I'm guessing bent yokes was more of a problem with vibration.
@harringtondav I don't think you need to worry to much about the u-joints. The only times I had to replace them was due to water in the bellows. Well that and (rarely) running to long with the tilt all the way up.
Volvo doesn't sell just the u-joints so you source them yourself. Be careful, u-joints come in different load ratings. So not only do you need to find the right size it needs to be strong enough to last. You have to do a "deep dive" on u-joints or trust some internet-idiot who may or might not know. I've found that no autos use these, commercial only.
I have replaced just the u-joints a few times, it can be done without pulling the shaft.
If your careful, have a u-joint press and know how and where to tappity-tap-tap as your pressing, it can save some big $$$. But if you screw it up ---- going to have vibration and increased bearing wear, and now costs more then if it was done right in the first place.
If your replacing the seal, this is a pretty technical job. Probably best left to someone has done this a few dozen times. I've trained a few techs and I kept a pretty close eye on them the first 3 times. Pretty easy to screw this job up.