[nu2-72]

You will want to remove the arm.
Remove the arm and be very careful to do this over a large clean surface. There is a disc under the arm.
Use air to push the assembly out of the bore. Remove the caliper seal.
The piston does have a LH or RH spiral center. You may remove it for piston and stem cleaning.
Install seals and re-assemble.
The reason for removal of complete assembly is because there is a rubber seal on the spiral post to prevent fluid leaks and the disc under the arm provides pressure against that seal. These parts will come in the new kit and should be used for a guarenteed seal job.
The arm has flats and can be repositioned after the assembly very easily.

DO NOT drive the piston out as the inner assembly is fragile. Use air only and it will pop right out.
Would pics help?