What would be the approximate cost of repair vs. replacement (we would prefer a gas dryer anyway)?
This repair will most likely be much cheaper than buying a replacement, unless you just want to make a jump to gas. First, check the venting for the dryer. Clogged venting can cause prolonged drying times. It could also be caused by a blown thermal fuse, bad heating element or high limit thermostat. If the venting is clear all the way to where it exhausts to the outside, then I would suspect bad thermal fuse or high limit thermostat. They can be tested using a multimeter or ohmmeter. It is best to replace both the thermal fuse and the high limit thermostat at the same time and they often come from the parts supplier as a set. I’ll attach a photo of a fuse/thermostat for reference. Really sorry for your trouble and I hope this helped some. Best wishes.