First of all, if it runs PathPilot it already has the Mesa control card - that's a good start. If you have access to the machine it shows the model version towards the bottom left on the PathPilot screen. That may not however be foolproof.
The first major upgrade for the series 1 machines was the VFD spindle control. Check in the cabinet to see if you have this device:
Attachment 422904
The other major upgrade would be the 3 phase stepper update. As far as I know all pre-series 3 stepper motors where painted (white) for protection. Series 3 stepper motors don't appear to need this sealing and are black.
Check out the upgrade requirement diagram here:
https://www.tormach.com/store/index....90&portrelay=1
Step