If yours is 'chirping', it might mean the windings are hitting the magnets and you'll need bushings too, and if it's that worn, the seal has suffered. And brushes...
Do you have a link for the jag kit? The seal someone sussed out was for a Honda. Search here - I remember seeing them on eBay, so they shouldn't be too hard to locate now, I think.
Are you sure the chirp isn't the groan a normal motor makes while it's running and building final pressure?
You might need to hold off until you get the entire unit out of the car so you can remove and disassemble the motor so you can see just what's wrong and if it can be saved, etc. If you want to shorten the process, perhaps you can locate a used motor and o'haul it first, so all you have to do it R & R the unit.
If you plan on replacing the accumulator, now's the time to start that hunt - check w/Victor at spinningwheels-sc.com