Hi Andrew,
although cleaning switches is always a good idea you would be better off applying a signal to the ant socket and measuring the receive sinad before you touch anything repair wise, you may find it only needs adjustment.
if you dont have the equipment to carry out such tests i would suggest getting someone else to check it and calibrate or repair it for you.
also be very careful if working on the inside of the unit with the case removed although the 900v rail is enclosed in the faraday cage there is still hundreds of volts available on the trimmer capacitors and several other places.
When working they are an excellent radio i have one im in the process of repairing myself.
