Most definitely file an in-game ticket about the hack ASAP, and either wipe the machine or unload all the anti-virus protection and scanning devices you can on it. (I prefer to just wipe the machine) Remember to include dates in your in-game ticket (i.e. I last used the account on <this> day and the password was changed on <this> day and I regained control of the account on <this> day) -- this can help the GM identify that indeed your account was not under your control if the hacker did anything nefarious while you were on it.

GMs can do restorations in order to get your gear/money back, but there will be an investigation involved and it will likely take a few weeks. Check the customer service forums (on a different computer, since you have to put your account name/password in there to log in) for help -- they have some stickies as well as GMs that can answer your questions.

Don't be surprised if you get a late ban for exploiting/spamming -- Blizzard often detects account compromise late and will ban the account for your (the original owner's) safety in case the hacker still has access to your account.