Tough for techs to give you a cost without seeing it. As mentioned most will look at it and quote you before doing the work but there is usually an hours labor charge if you decide not to go forward. The guy in Newport might be a good option If you can drive down and drop it off and he is willing to give you a quote. I think I spoke to Urban years ago and found him high. Terry Dewick repaired a radio for me for a very reasonable cost even when factoring in the shipping. I have also had work done by the techs at John's TV in Taunton. They fixed a Panasonic receiver for me. Cannot recall the cost exactly but believe it was around $120. Sounds like your issue is the switch. A friend who I discussed a similar issue with and knows electronics said the a/b switch can be the culprit. Might just need a good cleaning with deoxite. I have also used the services of Atlantic Systems in Hanover but that was too long ago to give you a referral but the fact they are still in business says something -
http://atlantic-systems.com/ This gives a breakdown on what you asked about -http://atlantic-systems.com/policies/