While driving the check engine light came on and my speedometer stopped working, what could be the possible problems? Can it be a do it yourself project or does it have to be done by a professional and is this gonna cost me an arm & leg?
The speed sensor most likely has a problem of some sort. It is one of the things the ECU monitors and if there is a problem with it a code is set and the CEL light comes on. You should find out what the code is to help determine what repair action is needed. The trouble may be due to just a loose connection to the sensor possibly. If you are fairly handy you should be able to fix this trouble yourself.
That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.
The light probably came on because the speedometer stopped working. The Vehicle Speed Sensor (VSS) might be the problem.
An arm, perhaps, but not a leg, too.