I've got an iPhone 3GS with a tethered blackra1n RC2 jailbreak that I want to get rid of (the JB, not the phone

). I've been out of the iPhone scene and I've even made this post before but this stuff moves so fast I feel like I should make it again, can someone help me with what I need to do to get off this tethered JB and get a better one going?
Should I use Spirit to re-jailbreak? I have access to a Mac if Pwnage Tool, or something else, is considered better. (If I don't think I'll have Mac access in two months, should I safe it and use a PC jailbreak I can run myself if something happens?)
I would really love to unlock the phone, but the first time I ever tried it with blackra1n, the phone was bricked, so I'm a little apprehensive now. My modem firmware is 05.11.07, can that one be unlocked safely and easily? How is unlocking done properly, is there a good guide somewhere?
What's the correct process for switching jailbreaks and basically "starting over"? Do I just restore and run the new jailbreak?
Finally, how do I back-up game saves? That's the only thing I have on there that feels irreplacable - I have my pics, music and phone numbers saved elsewhere. I've gone in via WinSCP before, but the folder structure makes no sense and it's impossible to tell what's some random app I deleted months ago and what's a game I'm 75% through at the moment. Is there a convenient way to back-up saves or should I just back up that entire folder?
My numbers:
Version 3.1.2 (7D11)
Modem firmware 05.11.07
I let Cydia backup my SHSH, if that matters for anything.
(Sorry about the big post, I've bricked an iPhone before and I'm out of warranty here so I really don't want to mess this up.
