A up Digger.
Of the 800 members here, Ill bet about 800(ish) have had to do this at some time.
Piston seals are quite easy to fit (assuming you've got the piston out!)
Just be sure to clean the square profile groove inside the caliper as any dirt left in here will cause it to happen again. Use something soft like a toothpick or a cocktail stick.
Steve