Fisrt, the service light comes on every 5000 it has been reset. It should only stay on for 2 minutes after start. Normally, there is no problem at all. Just needs to get an oil change, maybe.
To Reset it, there is a plug just under the odometer. Remove it, and with a pen push the buttom til you hear it click. If it doesn't click the light will continue to come on.

Next, bulb light indicator could mean a couple of things. Most of the time it could just mean, one of your bulbs needs to be replaced. Replaced them in pairs, you will have another bulb out light if not. The current needs to match.
That is reason #2.
Another reason, is your bulb sensor relay is defective, you can either re-solder it, or buy a new or used one.
I think that is the final reason. Could be another or two, but the only big problem could be no headlights, and that could be Bulb Sensor Relay, Headlight Relay, Bad headlamp(s), or corrosion at headlamps.

Your last question was about timing belt. If you change it, get the upper seal done, and the crankshaft pulley checked out. If chankshaft pulley seperates, which it will eventually, mine did at 190K, its easier to do it at timing belt change because you have to remove it anyway. But I would probably hold out about 160K or so, and do all these pieces.