Yes, you will disturb the cams and no, it is not that big of a deal. The liquid sealer that Volvo uses in that application is pretty good stuff but it will leak after some time. The 16V motors were refered to as "oil leaking, wallet biting, eyesores" back in the day. They can be a high maintenance pig but they are really not that tough to work on. The big thing with the liquid sealer is cleanliness, keep it all really clean and if you can use a liquid stripper to pull the old stuff up, keep track of the lifters and the holes that they came out of and when you put them back in line up the hole in the lifter with the oil feed hole in the cam carrier. Don't ask me why but it sure seems to make a huge difference in the amount of time it takes for the whole deal to oil up and quit ticking on that initial start up after the repair. If it were in my shop or my vehicle I would just go through the whole darn thing which means new belts, reseal the cam carrier, all new crank, cam, and counter balance shaft seals, change up oil pump bolt, and any new cam belt covers and miscellaneous crap that it needs. Yes, it is a big job and expensive but it is really not that complicated or involved. I don't do them all that often but I did do my daughter's car a couple of years back and it looked perfect when it was in last week.

Have fun,
Mark