I believe your 2 problems are unrelated. Light bulbs in the climate control system sometime burnout. There is one in the fan speed selection switch and there are two on the top of the unit that lights up the buttons. You need to pull out the climate control unit to get access to them.
Air is directed to the top of the dash, the vents, and the floor using vacuum controlled doors. When you have no vacuum, the default is "defrost" and from my past experience, I found the problem in the engine compartment, before the vacuum makes it to the climate control unit. Trace the vacuum hose from where it passes through the firewall (passenger side, near the relays and a/c evaporator) to the tee junction ( near the mid point of the firewall and looks like a saucer with a tube going out the bottom and branches into 2 connectors with the bottom one feeding the vacuum to the climate control unit. It is secured under the wiper assembly with a nut). The tee junction may be broken or the bottom hose may have been pulled off. Check the vacuum hose for nicks or holes. Failing that, the vacuum connector on the back of the climate control unit may be off (can happen if someone popped out the climate control unit or radio).
Check those out. If that didn't work, post your findings and you might need to be lead through the next phase which is more complicated - tracing the red, white, and blue vacuum hoses, checking the 3 vacuum motors, and seeing if the doors are binding.
Good luck.