Welcome aboard. Excellent post btw. The only couple of things I can see you asked about but perhaps weren't covered in the excellent posts above are:
Manila – don’t know how to identify (HELP!)
You're running stock right now, so that's Manila (aka TF3D) 2.1. There are some ROMs with 2.5 as you've probably discovered, but do some research on the pros and cons of 2.5 e.g. no landscape, MMS issues, etc. I'm using 2.5 right now, and don't know if this works in 2.1, but if you go to Settings | About Phone | Software Information, your current manila version will be shown there.
Do I need to unlock, why or why not?
If you're referring to the HardSPL (HSPL / unlocker) and not a screen lock, then by default all phones are locked from factory so that you cannot flash a custom ROM. You unlock them so that you can. As the first response above indicated though, if at any point in time you're going to take your phone in for service or send it back for any reason you should a) download your stock carrier ROM from
here i.e. the one it came with when you first used it, b) flash back to that ROM, and c) apply the relocker (instructions found
here). That way your carrier won't know you've been "tinkering"
