How about on aan HP Pavillion zd8000 laptop?
What Linux would I use to replace "XP"? Would I be able to run Microsoft Office? Would it play the Pirate Galaxy.com game and run RaidCall.com?
"What Linux". As you are used to XP I suggest Linux Mint with the Mate...
"Would I be able to run Microsoft Office" The simple answer is no. Both Mint and Zorin use LibreOffice which comes for free and can read and write MS Office document files.
The answer to your other 2 questions is that it is possible but not easy.