Cleaning/Reconditioning Costs

If I were to purchase a 5D (~$1000) from ebay (or anywhere else for that matter) and turns out it needs a trip to CPS for cleaning/reconditionin​g/both, how much (ballpark) would that cost?

Even if there is nothing wrong with it, I might still send it for cleaning and lubing (if its <= $200) unless you guys say that would be a bad idea; in which case, I'll break down and learn sensor cleaning and buy some cleaning equipment for DIY later.

Also, if one purchases a device without the warranty card/box/receipt, how do you tell if its legit? Will CPS tell you who its registered to if provided with a serial number?

I dont really understand what you are asking?
If you get a good deal and the pictures show up dust then yes, if you want it checked then yes they strip it and check it and all this for labour plus parts. They will send you a quote but with a serial number you can get any history that they have done.