I would do all the things I could myself to save the money for the absolute neccesary things you must buy like the air filters, tires, good shocks, some new front brake parts (CX are known for a weak front brake) If I were on a budget for braking I'd get the CX650 dual piston caliper and bracket, cross drill the rotor, buy some EBC or Galfer pads, and get a quality stainless steel line and call it good. The control cables should be shortened, it's not that bad to do yourself. To clean the engine you can soda blast it in your driveway if you have an air compressor, a Harbor Freight blow gun and a 3ft piece of clear tubing 3/8" diameter I think? Harley mufflers are a good way to go and yes, you should have a crossover tube. IMO.
Cheers, 50gary
Cheers, 50gary