Datateck - it seems you are havinga rough time with your P38 sorry to hear this- try the link below
Heater Core O-Ring Replacement
I found this very useful - got extra set of "o" ring just incase & changed the temp sensor - that said I did cut out the air duct and put back with duck tape to help with access - in facttook longer to cut duct than do the job - anoth pair of hands help when reassembling pipes back to keep square holding from engine bay - did not need to remove radio
Hiya, If its the alpine unit I have the keys and happy to lend them out
Data - I owe you one anyway, PM me your address if you'd like to borrow them and I'll send them over.
Cheers
Marc