1996 geo 1.3L automatic

[91-93-96Geoman]

Hello all,
I have a 96 Geo Metro with 1.3L engine and auto tranny.
I get Code P0758, which indicates a transmission solonoid.
I clear it, the "check engine" light turns off until i start to drive again and once i reach about 15-20 miles per hour it turns back on again.

Anyone know where these solonoids are 1) located and 2) how to check and or replace them?
I don't see any "pots" mounted externally on the tranny, so I am guessing they are internal and under the metal cover on the side of the tranny.

My haynes repair manual is worthless in many instances, which includes this one.

[Johnny Mullet]

Solenoid Testing Page