Jen,

 I have to agree. I've done this on 3 Vanagons by the third one I just
replaced both the master and slave since the one I didn't replace went a few
weeks later.  I wouldn't try to hold the fluid in the line because you'll
have to bleed the system anyway. Just make sure you catch as much of the
fluid as you can.  Rebuild kits are less expensive than a new cylinder (but
an even bigger joke when you give them a lot of money for 3 pieces of rubber).

Blitz