....
you're screwed
I saw a video on youtube that tested speed for 3g v 3gs and 3g vs iphone 4
a freshly jailbroken 3g still hangs on 'reloading data' as its THAT slow
so removing stuff if you've already jailbroken does nothing. I think you should just use it for music and go buy a 3gs or wait for iphone 5 this october
Or give a "upyours" to apple and get a better and faster phone with a bigger screen
Or use 'terminal' and try to update cydia manually, i think you need to ssh and update files manually too