Hehehe, get a can of block sealer :)
Bar's leaks is supposed to be good, I've used kb or k&b block sealant, and it worked well until i blew the gasket completely out.
Trick about the block sealers is that you hafta follow the directions, otherwise it won't work. My problem was a worn out freeze plug (actually, it had a small hole in it, never figured that one out), and it worked well, so i'd assume it would work fine for your application as well.

If you want to replace the gasket, thats another story. Its a straight forward job, provided you have the right tools, its not hard but it can seem rather intimidating. It's a good weekend's worth of work if you've never done one. You'll need a good torque wrench, and you'll probably want to go ahead and replace the head bolts(the whole set of ten should only run about 30-40 bucks)
a new head gasket is about 45 bucks (or 20 or so from bimmerparts.com)
A head gasket is like replacing intake and exhaust gaskets and doing a timing belt all at once. If you do decide to replace it, you will need to replace the intake and exhaust gaskets, otherwise you'll have an exhaust leak.

Personally, i'd try the block sealer first. If you follow the directions, it works well. Your coolant might look a little funky, but you can flush it out a few times with water and it'll go back to normal. It wont cause the car to over heat.
Good luck!