Have radio code, need more...

I've reset this radio before no problem, but not this time.

It's a 98 Jetta GL 2.slow. I was too lazy to go inside and get the
number, thought I could remember it,
put wrong code in. Now says '2 Safe'. Googling, I found where it said to
press key combo Mode+Scan to
reset. My radio doesn't have a 'Mode' button. I tried other buttons, no go.
It's the original radio, Clarion I believe. After a battery disconnect I
tried to enter the code
from memory a couple of times, and now it says "2 Safe". After getting
the right code which I've used
before, I tried disconnecting the battery for about 24 hrs and pulling
the radio Fuse for about a week,
it still won't even allow me to enter the code, just say's "2 Safe". Did
I kill it?

I guess my real question is: Can I put in a Pioneer or something? Is the
alarm system or anything else
dependant upon that original radio being there?

Thanks,
Les