Should be the same (up to 2000). There are brackets that attach and replace bolts on the hatch, and should be some double sided tape as well. not a big deal.

I would have it painted at a local shop, with your volvo's color, unless you have some real painting equipment (and ability).

Clear coat will need to be applied, and it is a highly visible part, so any goof-ups will show and you will see it all the time, if you go the spray can route. Of course, a good job is possible that way, but it's up to you.

If you were touching up a scrape on the lip of the front fascia, a spray can is fine. This is different.

Be sure to bring the V70 to pick up the spoiler when its ready, so you can compare it in its place vs the roof to see if it matches.