How to replace a heater fan motor, is it changeable from the engine compartment?

No, but it isn't too hard to get to under dash. I will paste instructions from autozone.com below. Pictures may not come thru.

CAUTION The Supplemental Inflatable Restraint (SIR) system must be disarmed before removing the blower motor assembly. Failure to do so may cause accidental deployment of the air bag, resulting in unnecessary SIR system repairs and/or personal injury.
Front Blower Motor
See Figures 1, 2 and 3

Fig. Fig. 1: The blower motor is located behind the glovebox, behind the blower motor cover

1. Disconnect and isolate the negative battery cable, then wait 2 minutes before proceeding with the removal. This will effectively disable the air bag system preventing possible personal injury.
2. Remove the glove box from the instrument panel.
3. Remove the A/C-heater blower motor cover.
4. Disconnect the blower motor wiring connector.
5. Remove the blower motor wiring grommet and feed the wiring through the blower motor housing.
6. Remove the bloweHow to replace a heater fan motor, is it - 0900c1528003c5d0.jpgews.

Fig. Fig. 2: Once the cover is removed, unplug the electrical connector and push it through the opening in the housing

Fig. Fig. 3: The blower motor is secured to the housing with three small screws

1. Allow the blower motor assembly to drop downward to clear the instrument panel and remove from vehicle.

1. Place the blower motor assembly into position on the A/C-heater unit and tighten the mounting screws.
2. Route the blower motor wiring through the blower motor housing and seat the wiring grommet in the hole of the blower motor housing.
3. Reconnect the blower motor electrical connector.
4. Install the A/C-heater blower motor cover.
5. Install the glove box into the instrument panel.
6. Reconnect the negative battery cable. Check blower motor operation.