Just clean it and buy new O-rings. My slave is 17 years old on the original O-rings. But I have cleaned it out and reassembled a couple times. I replaced my MC with a new Wilwood, I believe it's 5/8" bore. If you flush and bleed every 2 years, you'll never have a problem.
The slave is either 3/4" or 7/8" bore, can't remember. Greg?
I believe travel should be around an inch at the slave, but I haven't measured it.