For the moment, I'm assuming pre-97. If it's 97+, I know nothing. "Half the dash" is a bit much. You need to remove the plastic bezel that covers the switches, instrument cluster, etc. this is held on by several screws that you will see if you look at it from below, and by some snaps that you cannot see, at the far right edge by the radio and heater. If it is a pre-95 the rest is easy. You remove that bezel (it flexes a little), pulling it out straight at the right edge, and under it you will see the heater control unit held on by a couple of screws. The bulb is a little "grain-of-wheat" bulb in a plastic holder inserted into the back of the unit. It's a fragile bayonet mount, with little plastic tabs that are ridiculously easy to break. If you break it, or if someone before has done so, you'll need to put it back on with tape or something. It will fall right out otherwise.
If it's a 95 or 96, you'll find it nearly impossible to get the bezel off without breaking it, owing to the fatter steering column. You pretty much have to remove the plastic jacket of the steering column to do this without breaking it, and even then it's a stretch. After a couple of radios, a cluster replacement, and a switch repair or two or three, I got tired of doing this on my 95, so I just went ahead and broke it. The crack, right above the steering column, is a small price to pay on a vehicle which would flood from the rust holes in the roof if there weren't bigger ones in the floor.
