A check engine light is also used to indicate to the driver that ur next major service is due so if ur car is at that point I'm not sure for American models as u use the imperial measurement system but over hear in Australia our first major service is 80,000km.
The first thing I would do is Reference the cars logbook and look at the schedule of intervaled services if u are in a major service interval period it will be a case of a qualified mechanic doing the manufacturers branded service. By taking it to the Car Makers preferred service provider to service and telling them about the issue u will make sure that they find out the what the error was fix it and they clear the error code code after. In terms of money for a service and the repair u can sign up to a daily deal website and get vouchers for services I have one for ultra tune for $29 and then u can find out what the code means no one said u had to fix it. if not warning lights if they are coded will display like this " " " " " " " " " " " " and keep repeating the " is referimg to a blink and the spaces a pause the code above would be what they call a 5 1 code and they can easily be referenced by a search through ur favourite search engine an example is a 5 1 code on a Ford Probe is an indication of a problem with the transaxle sensor which is either an easy fix or or one of the most expensive there rarely with cars is a happy medium.
The warning light you might find after reading ur glovebox handbook isn't on for that purpose, so go to the section on information about the dashboard display and have a look at what it says that light is meant to indicate. It will probably tell u to take it to a qualified mechanic but it may also tell u it is a fault of a paticular mechanical operation the car performs.
There is however one final thing u can do and it is either buy a tear down and rebuild manual on that model car, (hear in Australia there called a Gregory's tear down and rebuild manual and there available at Repco and Supercheap Auto or online) this will walk u through what the most common likely issue is and show u how to fix it, at least in this way if it is at a level u think that is achievable for yourself to complete u can save some money and do it yourself.
I cannot recommend these books more because if u love ur car and / or want to learn about cars , they will give u a picture of the part a detailed how to take a part step by step process along with the rebuild process, also by reading the book u will learn how to do the easier things like change ur breaks, draining of fluids and replacement, correct wiring diagrams and handy hints and tips. Basically if u learn a couple of things u can then apply them to most other cars like break pads which apart from different sizes and shapes is a process duplicated among all cars. Another great thing to learn paticularly if ur car isn't receiving a regular logbook service is servicing that vehicle yourself which is another process similar across many makes and models.
U can always search the net for how to videos on YouTube and find out how to do simple servicing tasks like changing breakpads along with error code keys. Rember u can always clear the code with a piece of wire and disconnecting ur battery if it isn't important look up clearing an error code on gmail.
i took it to autozone the code they gave me was the gas cap code but it keep comming on, i check the gas millage and its getting 23city not highway but at the moment im un employed and cant aford the dignostic will this problem become bigger?