I bought a new compressor for mine for the same reason. I thing t was 300+, but it has worked flawlessly for 5 or 6 years. Everyone I know with a $100 compressor replaces it at least once a year, so I figure I came out ahead.
Basically you need to do what everyone said. Replace your o-rings, make sure you have good hoses, flush everything out, get the retrofit R134 fittings, replace the drier/accumulator, vacuum it down, and fill it with oil and refrigerant. That's the short version. Your mileage may vary.
Slonaker