can you fix a bad valve?

I was told at Brake Masters that I had a bad (stuck) valve on my compressor. They said that I would have to replace the compressor, drier, accumulator as well to warranty the work. $1000 later, everything would be kosher. Is this true? I have found the items I need for about $300, and a friend to install everything, but is there a way to un-stick the valve? The report said my low side should be 30psi and it was at 100psi. Any help would be great.