The official OTA for the GSM version of the original Galaxy Tab just started rolling out, and Chainfire over at the XDA forums has already pulled the update, rooted it, and made it available for your downloading pleasure. There are two different versions of the download - one with a new bootloader and one without. While I didn't read the entire thread, it appears that most users had better luck with the version that includes the bootloader.
If you're concerned about flashing a ROM that includes a new bootloader, fret not - it's signed, but not secured. That means you'll still be able to flash custom kernels, ROMs, etc.
For the full skinny, including download links and installation instructions, head over to the source thread on XDA.