1) You can use any radio in this thread:
http://forum.ppcgeeks.com/showthread...ighlight=radio - these are CDMA radios that are compatible with the Touch Pro.
2) Always a chance you could brick your phone / GPS. Not likely if you follow insturctions.
3) Radio upgrades impact all communictions within the device - so yes, data is impacted but I wouldn't expect any particular problem to be resolved as your current TELUS radio is probably the most up-to-date.
4) Short answer - No.
You say that you have 1.03 on your device now. Are you sure of this? The version sent out with TELUS devices was v1.07.02V to my knoweldge - I could be wrong though.