If it works well as is - leave it alone.
I had sent a CT Seven to HiTech for a full "refresh." Rolland does very good work but these services are now offered by Greg ON THIS SITE.
I didn't realize that a "full refresh" only included replacing the power supply caps and an IC. I was under the impression that ALL capacitors
would be replaced... not the case.
Opening the cover you can be overwhelmed by the number of capacitors used. Had I known it was just the PS - I would have done the work myself!
Tuners MAY need to be re-aligned after working on the tuner board... there are conflicting opinions on this subject.
This takes specific equipment and knowledge.