You could look into bypassing the heater system with an aftermarket system like this, since
it appears to be a recurring problem with the OEM system:
https://www.youtube.com/watch?v=gDCpZa5dJk4However from what I have read, these aftermarket electric heaters don't put out a lot of heat.
BTW, if you decide to go this route, I would insert a fuse right near the battery connection
instead of on the heater, since you could short-circuit the battery and cause a fire if the cable
wore through and got shorted to ground.
A few more alternatives would be to:
1) Install aftermarket heated seats. These seem to get better Amazon reviews than the car heaters.
2) Attach aftermarket fans to suck out the heat from the dash vents. Not sure how well this would work.
3) Go back to the mechanic and ask if they can repair the problem again at a discount since they did not
make a permanent repair. Many shops will offer some kind of warranty for the work they do.
Check your receipt for the fine print.
4) Find a mechanic who has successfully solved this recurring problem with an aftermarket blower fan
replacement and avoid installing the OEM parts again. This part looks like it could work for your vehicle,
but please double-check:
https://www.amazon.com/ECCPP-Plastic-Resistor-2001-2004-2001-2003/dp/B073VLJFSN/ref=sr_1_1?s=automotive&ie=UTF8&qid=1525377639&vehicle=2001-40-299------------1-0&sr=1-1&ymm=2001%3Adodge%3Adakota&keywords=heater+fanFrom the reviews on this part, it sounds like it may have solved this recurring problem.
Some mechanics get very offended if you ask them to install parts you bought, so ask nicely and don't
assume they will do it.
Personally I would not sell a reliable vehicle like yours that had a heater problem, but I live in a much
warmer climate in Texas where lack of heat would not be a major issue.