Chrysler Repair: 1993 Chrysler Town and Country ABS recall, brake fluid reservoir, chrysler town and country

Question
My brakes recently went out - ABS light on, I drove it to Olympia, WA Chrysler dealer having to severely press on the pedal. The shop replaced the ABS components under the recall, but said my master cylinder was shot and attributed it to contaminated brake fluid - either very old or someone along the way put in wrong fluid. The chemical "litmus " test showed severe discoloration within minutes. They note all my calipers, boots, anything rubber would need to be replaced because of the defective rubber (I noticed that the rubber boot on the brake fluid reservoir cap was swollen, but the shop said they didn't check anything else and asserted the industry standard was that when this is observed, they change everything.
My question - that I am not satisfied with - is even if there was contamination, couldn't the master cylinder failure be a result of the excessive breaking I had to make when the ABS went out? Was it just coincidental that they would fail at the same time and the dealer says that the master cylinder failure was caused by faulty brake fluid. So they replaced they ABS recall items but left me with a car that can't ride on the street.  The master cylinder for this model (Bendix 10 ABS) costs $2,500 - which is greater than the value of the car. The reason I am pursuing fixing it is because I put in a new transmission 6 months ago, it runs great, looks good and has about 154,000 miles.
Would you advise that I have a valid argument that it is not coincidental (master cylinder failure and ABS failure) or should I just get it fixed at my expense (total $4,000).
I am thinking I could track down a used master cylinder if that is advisable and doing all the fluching and rubber replacment myself- I could never afford that dealer cost for repairs. IS this tpy eof master cylinder repari and replace difficult - I have done old school master clinders in basic pickups and cars?  
What do you think Kevin.  Thanks


Answer
they can only do what the recall calls for and that would be the pump and master piston. Anything past that Chrysler does not cover because those are the known parts that were recalled for. What else did they replace??  When i do the recall I do a dual function switch and the accumulator along with the pinion and abs pump.