Its not hard to rebild calipres.
A kit is around $15 and replaces the rubbers, you also grease the slides and I also replace the fluid annually.
Its not rocket science but you really need to understand the braking system, have a big container of white spirits, a clean environment and some patience. Istarted doing this after sitting outside a mechanics workshop and watching hime do mine, it took about 40 minutes per side, then bleeding took about 10 minutes, then he charges me $400 for a full rear brake service. The same service takes me less time and costs around $85 for the kits, pads and a new bottle of high quality fluid.
A Gregorys or Haynes go through it step by step.