Really, the only benefit with .602, is the upgraded baseband. Unfortunately, the only way to get the new baseband to install is to go back to Froyo, then install .602.
If you have the TBH app, you can download the 2.2.1 All in one installer and the .602 all in one installer.
Wipe data, cache and dalvik cache, go to mounts and storage and format the system, then manually mount. Then install the 2.2.1 zip. When that's finished, install the .602 all in one zip right after without rebooting.
If you don't buy the app, you can sbf using the links in my signature, then download and install the rooted .602 files from TBH. Or you can sbf and install the OTA update and use Super One Click root to root it.