Need some clarification on restoring, upgrading jailbreak,etc

[chkw94]

With new firmwares being released (4.1, and soon 4.2), I want to upgrade my firmware and still have a jailbroken phone. My current firmware is 4.0.1 on a 3GS. I jailbroke through jailbreakme.com

First, what would I need to do in order to upgrade firmware and have a jailbroken iphone on that new firmware?
Do I have to restore the phone, re-jailbreak with the appropriate program, then reinstall all my Cydia apps?

And secondly, what exactly are SHSH? I have heard that if I need to restore my phone, I must restore by downloading firmware, shift+restoring, using this tiny umbrella " program. I do not know what any of these really mean

Thanks, I would really appreciate some clarification.

[iYeow]

Every jailbreak must use a stock firmware. To answer your first question, yes you need to rejailbreak each you want an upgrade.
You do not need to know what exactly is shsh, all you need to know is an important file needed to do any stock firmware restore for most new idevices