Im not sure I would tell a noob to go to WM6 as it is stil in testing phase and bugs are still being reported and found. The overall co-existance with 3rd party apps just isnt fully there yet. I do agree with getting a clean ROM so have freed room however.
So I say that to say this, my vote is on Kirvins Clean & Simple 3.5 1.02 which can be found
here.
JAD and JAR require something like Midlet Manager