What you should be told is if the em hasn't been totally gone through recently and has been sitting unplayed for months, fixing just one or two problems may get it playing, but additional problems may well occur with additional play. Resulting in the need for additional service calls.
To totally go through a 4 player Surf Champ could easily take 4-10 hours and could easily cost $500-$700, maybe more if your repair guy charges more. But that might be the smarter move if you aren't able to tinker with the game yourself. Hourly rates can run anywhere from $50 to $150, including travel time. Parts extra! Also some techs really know em's and can track down many problems quickly. Others who work more on digital games can spend hours on the same problem. Look for someone who routinely works on ems.