generally your hboot and radio don't matter, but if you are a recent "rooter", you have the most up to date hboot and radio which is all you need for any recent rom.
There is guides in the root sticky on how to flash roms and how to make a nandroid.
But basically, to make a nandroid, all you do is boot into recovery, which can easily be done from rom manager. Then you select the backup and restore option. when in recovery, you use the volume keys to highlight and press down on the trackball to choose the highlighted selection.
If your selected rom is ever updated, you can install the update the same way you originally installed the rom, except you generally do not have to wipe the data (factory reset).
Installing roms is best done directly from recovery. You should always wipe data, wipe cache, and go into the advanced section and wipe dalvik (a few times each). Some roms will also have further instructions on their forum download page over at xda forums. Then you choose the option to install file from .zip
You will want to also read into the root sticky on the titanium backup tips.