Welcome to the world of Mac!
For openOffice, you could try this Mac porting of it:
Neooffice
If you want it now, you'll have to stump up $10 for the Intel version. It will be free from July 1st. It's a lot easier to deal with than the other port of openOffice, much more "Apple".
Microsoft Office 2004 for Mac will work fine on your MacBook. Don't forget that if you don't need a spreadsheet, iWork, including Pages and Keynote will read and write Word and Powerpoint files. You get the added bonus that they are easier to use and have some more powerful features (epecially Keynote).