New seals or just replace my master Cylinder?, Pretty new but leaking like a sieve. Options

[JRust]

Here is the story. I replaced my brake Master Cylinder last year with a 19mm. Worked great but started leaking badly in september. I was a little busy so I took it to a buddies shop to replace the seals & figure out what happened. It was leaking where the feed tubes come in from the top. He had it 2 days & said he was having trouble getting new seals. He told me he swiped some off a used car he had & all was well. I pick it up after hours & he says no charge. I have done some work with him & given him some deals on parts. So I say thanks. I then go on the falling leaf tour. My brake lights were stuck on all day. My pedal got a little on the mushy side as the day progressed.

Fast forward to now. My brake fluid reservoir is empty. I refill it only to have it all leak out on the floor under my car. It takes a bit of sitting before it leaks out. I ordered replacement seals for my current MC. Any tricks to replacing them? I also bought another new 19mm master cylinder just in case. Should I just install the new one & not worry about my old one (which has maybe 1000 miles on it)? Also the brake light being stuck on was an issue before although I fixed it. Now I can't remember how. Seems like I had to pull the plug on the side of the master cylinder with the wires on it. That reset everything & then the light worked as it should.

Once I do either any tricks to reseating the feed tubes properly? Thanks