I bought a used fully rigid Diamondback Response for $150. Everything is in great condition as it was only ridden about a dozen times. Breaks are great and it has all Shimano parts. I want to take it in for a tune up and my local Sports Authority does the basic for $35 and major tune up for $45. Would this be okay or is it really necessary to pay the $70-$90 at the smaller shops? I'm using the bike for riding around in my spare time and taking it on light dirt and gravel trails.