I'd highly recommend that you do pull the dash. It's really very easy to do and it will give you complete access to everything. If I were you, I'd plan for a day's work and in addition to fixing the previous owner's buffoonery, go ahead and clean ALL the electrical connections and make sure all the connectors are in good shape and tight. You might even consider removing and cleaning the heater box assembly. You might be surprised at how much crud there is in there. Might even make the air coming out of there smell better this winter.