KPB and KPH are Both 2.3.4

KPB is officially for asia-pacific

KPH is for europe.

for firmware upgrade, anything on the SD card is not changed (i.e. your pictures, files etc are not touched at all).

on your phone, if you have done a sync to your google account, all your contacts should be there.

for apps, you should be able to reinstall them from android market.
a better approach may be to go to android market, download an app called 'appsaver' which allows you to backup all your existing apps to your SD card. You can reinstall them after you upgrade firmware.

The ONLY thing that you can potentially lose is your sms/mms. But help is at hand! go to android market again and look for a free app called ' SMS backup restore". it should backup ur sms/mms to SD card also which u can restore after firmware upgrade

p/s: sorry to be so long-winded.. trying to give u as much info as possible

Wouldn't it be easier to take it to Samsung Service Centre to upgrade. Go during off peak (ie not lunch hour). You need to back up all the data. If you have a gmail account sync the contact to your gmail accounts. After upgrade you can sync back the contact from gmail to the phone. SMS can be back-up by using the apps SMS Backup and restore. Apps can be reinstalled if you have the apk files.