Leaky Master Cylinder Questions?

[Chad Frederick <fredie@u.washington.edu>]

Hey,
Resently my master cylinder on my 86 4kcs Q has began leaking break fluid.
It just started and only leaked a little bit and has just been getting
worse.  I keep putting off fixing it because I have no experience in this
area...yet.  But as this car is teaching my how to fix just about
everything on it.  
	I was wondering for those of you who are familiar with these problems, do
I have to replace the whole master cylinder or can I just replace the
gasket?  I really cannot tell just by looking at it where it is leaking
from.  I tried cleaning it but it was still hard to tell.  If I do need a
new master cylinder, how much is a rebuilt/good used one run. I can see
small puddles below the master cylinder after the car has been sitting for
awhile. The brakes still work as good as the stock brakes can.  Please help
me out as always with your guys input.

Thanks You,
Chad Frederick
86 4kcs Q