Q: How to backup, reformat and restore boot drive?

Bear with me, I am not a seasoned Mac person - I learned on PC's - any notion of reformating my boot drive makes me very anxious. Computer: Mac Pro (2008 vintage) running Snow Leopard, 10.6.8, 6GB RAM, 4 internal HD's (320GB, 1, 2 and 3TB).

Symptoms: Mac Pro starts with the horizontal "thermometer" bar across the bottom of the screen. It takes 10 minutes or so to boot, then starts over one more time, or several times more, but eventually boots up. I ran the disk utility repair from the install disk and it says HD is corrupt and needs to be reformatted, "incorrect..thread count" message in red seems to be the killer.

Plan: 1) back up boot drive to other internal drive using Time Machine, 2) reformat boot drive (320GB original drive), 3) restore boot drive.

I'm currently running Time Machine and doing a backup of the boot drive. Once that is complete I want to reformat that drive, which hopefully will repair it, and then restore it AS WAS. I understand from reading other posts that Time Machine does it all: after refromatting, install the Mountain Lion install disk, run Utilities, and simply do a restore. I haven't been through all of the steps, obviously, so I'm anxious. Does this really work? What else should I do in preparation for this process? I'm not prepared to go and spend money on stuff I don't need. If the disk doesn't repair, I plan on using one of the oher internal HD's, but they all have a bunch of files on them.

If necessary, can I do a restore to one of those HD's without losing any files exisiting on them?

Perhaps it it is recommended to use one of the other internal HD's as the boot drive anyway?

Whats' the best plan forward that might be different from what I plan?

I appreciate the helpful reponses, however, I have read some responses from folks who obviously know everything there is to know about Mac's and I sometimes I understand, but sometimes I have a vague idea what they are talking about.