hi Rich
Have a read of this for a good cheapish code reader
BMW Fault code reader options
As for writing the ECU, Im not sure if there is a tool that is within a sensible price range that will rewrite it.
not wanting to patronise, but are you sure you actually have the ability to remap your own ecu?
after decoding the Me 9.2 that is..and workign out all the maps??
The time and labour versus reward factor is VERy low for one remap....you would save yourself a LOT of grief by paying a pro remapper to do it!
If your very keen buy Optican (about ÂŁ3k ish

)...
Or you could always use an eprom burner and burn direct to the eprom (needs ECu splitting) as opposed to using the OBD2 port