brake pedal is spongy

[Brando8844]

Okay I have a 1995 V6 no abs 2wd auto t100 1/2 ton 123,606 miles

few weeks ago my brake light came on, i checked my fluid level and it was low. i added more knowing my brake pads were wearing and thats why the reservior was low.
so
I change brake pads. when I press the caliper back in, the fluid runs out from the reservoir cap. not what I had expected but whatever i guess...

I put everything back together and I press the brake pedal, it goes to the floor.
I press the pedal more to build pressure. its spongy for a couple inches then finally grabs.

I took it to the shop today. I had the guy check them, I asked him to bleed the brakes eventhough im shure thats not the problem. he also adjusted the rear brakes.
Its a little better but i dont think its like it used to be.

bottom line, he thinks I may have pressed some junk into the master cylinder when the fluid ran back through. Master cylinders are kinds high to replace for no reason. anyone know anything that might help?

This truck is awesome, ive replaced the starter once thats it... need to change the trans fluid and filter though.