Did all the bulbs go out at the same time? If so - the dash light dimmer switch (rheostat...
Did all the bulbs go out at the same time? If so - the dash light dimmer switch (rheostat) may have gone bad on your car, or perhaps it was adjusted on accident. The dash dimmer is the left knob on the instrument cluster - if I remember correctly, if its rotated all the way clockwise, you will get the full dash brightness when the headlights are on. The light on the shifter is not affected by the dimmer switch. Might want to check this before tearing into your car to replace bulbs. To replace this, you have to remove the instrument cluster (see below). Its located at the bottom, and held in by one phillips screw. It pulls out of its socket once the screw is removed.
If a bulb has burned out - the bulbs in the instrument cluster are not too bad to replace. The easiest way to remove the instrument cluster is to remove the knee panel under the steering column, then reach up and 'push' the instrument cluster out of its opening. You'll probably have to disconnect the speedometer cable, the oil pressure guage (10mm nut), and maybe some electrical connectors as well in order to pull the cluster out far enough to work on it. The bulbs are on the back of the instrument cluster - there are two, located near the top. Twist the little bulb holders, then remove them to reveal the bulb. The bulbs simply pull out of the bulb holders.
The bulbs in the climate control panel aren't too horribly bad to replace either - it involves removing the wood trim piece around the climate control, then removing the climate control panel 'face' (its clipped on at the sides). From there there will be 3 bulbs visible - and you can carefully pull them out at this point. This is assuming that you've got the panel with the buttons arranged vertically.
The bulb for the other switches like the rear dome light, antenna, sunroof, and rear defogger is a bit harder to get to on the '77-'80 models. The bulb is located behind the climate control panel assembly. It is just a single bulb, the light is distributed to the switches via fiber-optics. The only way I've been able to access this successfully is to remove the entire center console. From there you can unbolt the climate control assembly, then finally access the one bulb for those switches! Not a fun job!
Anyway I hope this helps you out. Let me know if you have any other questions!