Amarin's response deserves the thumbs up. It is clear this is help from someone who's been there and done that, and done it well.

I have nothing to add to this excellent walk-through of replacement. My only excuse for posting here, is the chance the proportioning valve diagnosis is hasty. I say that from recent experience of my own, where the owner of the car was quite convinced the valve was the problem, but instead it just represented the last place on the car for the brake fluid to collect from a leaky master reservoir. The plastic reservoir was cracked at the outlet port -- a much easier fix indeed. This was a 240.

Again, it is rare to see such a clear guide to brake line work, especially the point about getting the nuts started in all that fluid. Kudos!
--
Art Benstein near Baltimore

You spend the first two years of their life teaching them to walk and talk. Then you spend the next sixteen telling them to sit down and shut up.