I need to replace my original head unit HU-611 and have read some info about getting errors after disconnecting the radio and climate control units.

Can someone explain to me the proper way to do this so I don't fudge it, that would be much appreciated.

Before I purchase the radio, does it have to be the same part number? I see a lot of different HU-611 and there seems to be a few different part numbers for these.

Previous owner spilled something and none of the radio search/scan buttons work.

Thanks!