I have a 1969 convertible, no AC, with a hardly visible heater controls back light (bulb does work). I'm assuming that the bulb is like the ones in the cluster and has a filter. Is there a way to get to this via the front? If I pull the knobs, is the face plate removable? I'd like to change that filter and/or maybe even replace bulb with LED if possible. Sometimes I get stuck on the simplest things and I have a feeling that this one is simple.