2006 Gen 2 Front AC/Heat/Blower not coming on at all

Our 2006 Toyota Sienna front AC and Heat and the Blower fan will not come on at all. The AC light does not turn on either. The Rear ac/heat comes on ok, but not real cold, but the heat does work fine in the rear. This problem began a few weeks ago when we took the van to the dealership for an oil change and to have them do a warranty repair on the air bag ( the air bag light was blinking). When they gave us our van back, the ac and blower would not turn on at all. We had a family member pick it up for us, so we did not notice until the next day that it was not working. We called the dealership and told them it was working fine when we gave it to them, so what happened? They said bring it in and they will look at it. So we brought it back to them, and they said it was nothing that they did wrong, but that it was an internal problem with the control head, and would be $1300 to fix. After speaking to management and complaining, they came down to the cost of the part, which they said would be $850. We cannot afford this right now, and have started trying to fix it ourselves. We first tried buying on ebay the entire AC/Heat control head/climate control part, and replaced it, but the front still did not work (the rear still worked). We then read on here about the fuses, and my husband tried that (switching the fuse with the horn fuse), but that did not help. A family member suggested checking into the resistor. Does anyone know what the problem may be, and how we could fix it? Any help would be greatly appreciated. Thank you in advance.