Thanks for the help with the spring. I managed to get it put together correctly but the motor is still not running reliably. After checking the contacts with an ohmmeter it looks like I have some bad windings.
Some serious studying of the assembly shows that it was not designed to be serviced. The brushes are held in plastic retainers that are attached to the bottom of the circuit board which itself covers the bushing and clip that holds the gear end of the motor shaft. After chiseling off the peened over mounting studs and goofing around with the wiring I pulled the circuit board off and removed the circlip holding the armature in place. I'm going to call Tampa Armature when they open on Monday and see if they will be willing to rewind such a small armature.
If I manage to get the armature rewound and put the whole thing back together I'll take some pictures of the dis and re assembly process and post a DIY somewhere.