I never use the on-screen keyboard hence the reason I got a the "touch pro" because the on-screen keyboard on the diamond was just too slow for me, I am a heavy texter :P
But I do know there are different styles of on-screen keyboards out there somewhere maybe search for "Keyboards for touch pro" or something along those lines and I'm sure you will get a better selection of keyboards.
Now intsalling them and replacing them with the current keyboard, i am not so sure about, you can give it a try though
Hope this little bit of info helps