Q&A

 Master

https://techinfo.toyota.com
This is Toyota's tech info system available to the dealers. "Regular" people can buy a brief subscription to look up service information for their vehicle but it is not what I would consider "cheap"... $15 per 2 days or 75/month

http://www.alldatadiy.com/
AllData is a very good resource and another information source used by professionals nationwide. It's 26.95 per year and has lots of diagnostic information.

Many Toyota specific message boards, or boards specific to the Tacoma/4Runner have DIY how-to threads, which can be very helpful with pictures taken by users.

Often in the case of heating and AC, mode door arms and/or actuators can fail. This will likely require some electrical knowledge in order to diagnose the failure point if the door or arm isn't obviously broken. Many of those individual parts are available from the dealer and most cases won't require the complete replacement of the HVAC housing.

By the way, if the housing needs to be completely removed, it is best to let a shop equipped with AC refrigerant tools to remove the housing because the AC Evaporator core contains the pressurized refrigerant.

hope this gives you something to go on!