Hi,
For my computerized Pfaff, it costs me $89 here in Vancouver, Wa. A regular non-computerized machine is about $69. If it isn't broke and costs too much to maintain, KEEP IT! A tune up is a small investment in the overall 'love' of your machine. I recently had to weigh that choice when I took my serger in for repair.
I paid $79 for cleaning and new blades. It runs like a charm. The learning curve on a new machine, not to mention the finances, was way too high at the time.
:) Lisa
P.S. Talk to the best mechanic you can. Don't be afraid to ask them for references or ask to see their work. I had some issues with one shop in Portland not doing the best job. So, I went to a big name sewing dealer (Pfaff - even before I got my Pfaff) and talked with their mechanics. Now I request one specific guy to do the work. He's usually backed up about 2 weeks all the time, but he is worth the wait.