your question : ‘am i being ripped off’ is subjective. You may feel like you’re getting ripped off, but if the car brakes fail due to a bad job, then you probably should have paid more! if you could do this work yourself, then it would in all likely hood cost around 100 to 200 dollars in parts. using the normal figuring doubling this too 200 to 400 bucks is what you can expect to pay for this. HOWEVER… the most amazing thing happens when you start to disassemble old stuff. New problems creep up, you find old rusted stuff and things break off, and you then need to dig further along to find good fittings, steel, and brackets to use. this eats up further cash, and before you know it your job has doubled in size/price and time. working under a car can be a time consuming way to spend $$, and sometimes you don’t ‘see’ the end picture until you are in WAY too deep $$ wise.
if it were me, i would try to get rid of this old car, enjoy your memories of your parents, and remember… they wouldn’t want you stuck on the side of the road in their old car either! just because it’s their old car doesn’t mean that you must be unsafe in it.