I overhauled my Sprague HP-200 wiper motors a few years ago when the driver-side became noticeably slower than the other side. Their O-rings were completely worn out, so a few dollars-worth of new O-rings, a thorough cleaning, and a liberal dose of Triflow lubricant got them both working smoothly and much quieter. One thing I did was to add an inline mister lubricator to each motor's air line so they now are always lubricated - what a difference! I used the 1/4" Harbor Fright misters but they're now discontinued, but a Norgren (at three times the price) is the next best alternative.
The air-operated washer pump did however defeat all my best efforts to make it work without squirting fluid back onto my leg while driving. I now have two cheapo (less than $20 each) electric pumps from Pep Boys, one for the original wiper arm nozzles, and the other for a new pair of nozzles above the windshield: there's no way any bugs will stay stuck on now! I managed to graft the original Sprague push knob onto a momentary-on push switch, so now it all looks and works like original.
Neither of these jobs was that hard, and the end results are well worth it. Well-lubricated air wiper motors with new O-rings may be all you need. Don't give up on them.
John