As gas grills become more and more complicated it can seem very daunting to attempt to repair one on your own. However the basic design of gas grills really hasn't changed that much. Sure, there may be five burners where there used to be one. But most all gas grills are a metal box, either stainless steel or cast aluminum with burners, regulators, ignitors, and fittings that are pretty similar to those grills of years gone by. Gas starts out either in your tank or if you have a natural gas grill attached to your home from the gas line. The gas passes through a regulator (to limit the gas pressure), through a manifold to divide it up between the burners, then through the control valves where you adjust the flow rate to control the temperature. From here it passes through the venturi tubes to mix with oxygen so it can burn and finally into the burners and out through the burner ports to make the visible flame. Above the burners you have some type of barrier that protects the burners and helps to distribute the heat. In the past this barrier was typically lava rocks or ceramic briquettes (that some grills still use). The barrier catches drippings from foods so they can be burned off by the heat of the grill.
Before you start pulling your grill apart be sure to open the lid, make sure that the fuel tank is in the off position and the gas disconnected. Propane and natural gas can be very bad for you whether there is an explosion or not.
Now you're ready to get to work on your grill. The first step is determining if it's better to fix or replace. This is pretty much a personal choice. Many of today's lower end grills are much lower in quality than grills built 10 years ago. The drive to keep down cost and bring up profits has lead many manufacturers to take shortcuts. Now you should be able to find parts for most any grill made in the past 10 to 20 years, so unless you have something very old or very unusual you will be able to get the parts you need online, though they may be very expensive. The big question you have to ask yourself is, "Does this grill meet my needs?" If the answer is yes then go on and get it fixed up. If the answer is no then you should start looking for a new gas grill.
When a gas grill is working properly the flame is evenly distributed through the burners, the flame itself is blue with yellow tips and it should heat quickly on the high setting. With all burners on you should not be able to notice a difference in heat anywhere on the cooking surface. If this isn't how your grill works then you probably have a problem. To get you started let's talk a little about the anatomy of your gas grill.