So i bought it, I’ve played every Halo game to date, except this little dancer! I can’t wait until i get it, but it should arrive Wednesday 
Back onto the topic, i got it for Vista, and i will most likely be satisfied with just the campaign alone, but i also want to have a taster of the online. So is it possible to still do online multiplayer on the PC version?
Yes, H2V Live MP is still functional. However, only player-hosted games or games on privately-owned servers are available, there is no Matchmaking, and there are no playlists, other than map/gametype rotation on privately-owned servers.
Incidentally, you might want to check out MonstrMoose. They have a collection of high-quality custom maps with custom weapons, and also host the MonstrMoose Main Menu Mod, which allows custom vehicles on certain maps.