Welcome to the forums!
But sorry for the circumstances.
It very much sounds like you tried to load a rom not specifically designed for your exact phone model.
Good news is that can often be fixed or recovered. Bad news is it will take a little effort.
Anyway - first rule - don't panic, things go worse when you panic.
I'm moving your post over to the rooting support forum for the i7500 - one of the folks there might be able to help you recover using Keis or Odin or whichever Samsung tool applies to your phone.
Please post any details you can remember about how you installed the update and where you got it so others know where to try to help.
If you don't get a good response within a day or so, please click on my name, send me a private message, and I'll see if I can't find someone to contact for you.
It's possible you have a brick, but let's see if we can't find a recovery first.
