I have recently bought a secondhand Nexus S which is already rooted and has an unidentified custom ROM installed. The notification drop down says Genexus at the bottom, and the other details are as per the screenshot below.
The battery life on it is appalling, so I'd like to get it back to stock and/or install CM7 on it to see whether that improves things (of course, it may be that it just needs a new battery, but I'm also a little nervous about it running a ROM I don't even know the name of). I also have a Motorola DEXT and maybe a ZTE Blade (Orange San Francisco) that I'd like to root and update at some point, but I'd rather start with something that should be a little easier!!
I'm competent with computers and smartphones (I have a degree in computing, albeit about 25 years old!), but I'm out of my depth with custom ROMs. And anyway, I dislike and distrust blindly following instructions without understanding what I'm doing.
On top of that, there is much discussion in forums, etc. about kernels, ROMs, and various other components many of whose glossary definitions I understand, but I have no feel for what they actually do on the phone, or how they interact with each other.
There's lots of information out there, but much of it assumes a level of understanding that I don't have, is disjointed and/or contradictory, or gives alternative methods for doing certain steps without any clues about the pros and cons of each. For instance, the CM instructions say you need to install the Android SDK on a PC. It also says that if all you want is Fastboot, you can read the instructions for ADB instead of the SDK installation instructions. However, the ADB instructions explicitly say that they assume you've already installed the SDK. On the other hand, the guy I bought the phone from seemed to thing that I could just install ClockWorkMod Recovery on the phone (another thing I don't really understand) and use that to install a custom ROM without involving a PC (or at least the SDK).
So, can anybody point me in the direction of (or write) some information that explains how all this works, and in the first instance, where I can get the original Nexus S 2.3.4 stock ROM from, and the simplest* way to install it and the Google Apps.
Once I've got my head round the basics, I'm open to suggestions about what to install, but it will need to be something that doesn't break A2DP or the ability to work as a WiFi hotspot, both of which I need.
I have already done a Titanium backup, and I gather that I should also do a Nandroid backup as part of the process when changing (rather than updating) ROMs. I have a Win7 laptop and an old WinXP netbook with pretty limited disk space that I can use, assuming a PC is required.
Thanks in advance to anyone who can help.
* Yes, I know that's probably going to get me a number of different opinions!