You have 2 separat eproblems here...

The dirty fluid just means the entire system needs a flush. Pop open the bleeder, and let the fluid run out, while constantly topping it off in the master cylinder. Sela it up, pump it a few times, and repeat. When completed, close the bleeder valve, make sure the fluid is topped off, and you should be good.

The slippage is just your old clutch wearing out. Time for a new one.

You might just want to nip everything in the bud all at once. Replace the master, slave, and rubber line for the clutch. Then replace the clutch. It will all be brand new then...

"A young man who does not have what it takes to perform military service is not likely to have what it takes to make a living." - John F. Kennedy

Proud owner of an 88 Montero (with a blown engine).