Getting the valve body out of the tranny is no big deal.
Taking it apart isn't either.
Putting it back together is another story.
There are numerous small parts to deal with most of which
will fall out before you have a chance to memorize their exact
location. If you have steady hand, good memory, clean working environment,
and a long week end to spare, by all means try it.
You will be on your own however. Even most VOLVO shops don't do this kind
of work so there will be no one to ask for help. If you can, get copies of tranny
service manuals before you start. Just in case.
Also, in addition to getting small rubber balls, also ask for a new paper gasket kit
for the valve body. No mater how careful you are going to be, you will tear some of
them. Good luck.