Outboard boat motor - shift solenoids need replacement? Cost to repair?

I'm thinking of buying an older (70's) Starcraft American Runabout with an 100hp evinrude outboard mtr. I was told the moto's stuck in forward gear and the shift solenoids need replacement. I was wondering what a mechanic might charge....ballpark figure .... I'm not sure of the age of motor. Also, how much is a tune-up on a boat motor?