Is there a special kit that's needed for a hydraulic hammer? If so, any idea how much they cost and how hard to install?
I'm a big fan of HKX. They have complete kits, including pilot system. I have installed lots of them and they have great tech support. One of the easier and most complete kits to install.
What about the price ?
Too many variables. Depends if you want strictly a one way circuit, as for a hammer, or add a diverter valve for bidirectional operation to add a pulverizer or shear. There are different pilot systems available for setting flow rates. You have to contact HKX for advice as to the kit you need. I only suggested HKX because I have seen some cheap kit that don't work right and that is a nightmare on the job. When your talking an excavator with a hammer your talking expensive equipment. You want it done right.