It is important that you check often that all your lights are working on your car. You can be pulled over and even handed a fine or points on your licence for driving around with a bulb out not to mention it can be very dangerous. If an exterior lightbulb goes on your car, it may be a while before you notice it. Some cars do have a warning system that tells you that a bulb has gone, but not always where. Ideally you should always check your lights when going on a long journey, especially if travelling at night.
Some cars are relatively easy to fit new bulbs where as others can even require the front bumper to be removed to allow you to get to it. If you do have to do this then you may have to take a trip to a garage for them to fit the bulb for you. The bulbs themselves are often not that expensive but the fitting can soon add up. Make sure you get a quote for the garage first before they fit it to know what sort of bill you can expect. If the other bulbs have not been changed in a while, it may be worth replacing others that are nearby at the same time to avoid having to pay again for labour charges just to access the bulbs.