Your cheapest route will be to find another used motor if you can get it form a salvage yard cheap enough and if you can do the repairs yourself, if you are going to keep the car and do not want anymore issues
then get a new motor and save the money by installing yourself or if you have a friend that is mechanical.
Here are the steps for replacment:
1990 Accord
1. Disconnect the negative battery cable. If so equipped, disable the Supplemental Restraint System (SRS).
2. Remove the glove box.
3. Remove the glove box frame (lower support)
4. If not equipped with air conditioning:
a. Remove the three screws and remove the heater duct.
b. Remove the blower mounting nuts. Unplug the wiring from the blower motor, resistor and recirculation control motor, then remove the blower assembly.
5. If equipped with air conditioning:
a. Lift the carpet in the passenger compartment. Remove the side cover (kick panel).
b. Remove the control unit bracket nuts; unplug the five connectors and remove the control unit bracket.
c. Remove the retaining band, then remove the blower lower covers. Do not break the tabs on the lower covers.
d. Remove the retaining nuts and remove the blower assembly.
To install:
6. Install the blower unit and tighten the retaining nuts.
7. On air conditioned vehicles:
a. Install the lower covers and the retaining band.
b. Install the control unit bracket and carefully engage the wiring connectors to their proper location.
c. Install the kick panel and reposition the carpet.
8. Connect the wiring to the blower assembly. For non-air conditioned vehicles, install the air duct and tighten the screws.
9. Install the glove box frame and install the glove box. Note that some of trim on the frame is held with 2-sided tape; replace the tape when reassembling as necessary.
10. If applicable, enable the SRS.
Connect the negative battery cable