@wellreadfred:
Nope, you can't upgrade a (FW 3.x) jailbreak without uninstalling it first

. Good news is, you probably don't need to update it ^^.
You can safely install the latest SS hack on top of the old, though

.
And none of that should prevent you from updating to 3.4

.
@AZImmortal:
Not really: Poking at it with a shell access, or trying to install a custom update package

.