Go to ANY radio shop (you know, places that fix and sell radios to police/fire/etc.) and take the RCM in and ask for a tech to reflow the solder on it.

This will cost you up to $50 or so - but probably more like $20 - MOST problems are cracked solder joints and this fixes them.

Unless a relay is pitted badly or has an open coil, there is no reason to replace the RCM.