Gas and electric ranges are very simple machines and because of this oven repairs on them are very basic. The main reason is because of how simple ranges are to disassemble. The largest problems with most ovens and ranges are connected with the supply and ignition of gas or, if it is an electric unit, it will be the heating element. If these are the problems; you will want to check with the connections and hoses supplying the gas. You may also want to contact a service professional to repair your range.
Other than these problems, the door gasket could be preventing your oven from heating your oven to the desired temperature. The best way to determine if your gasket is bad is to turn the oven on and feel around the door of the oven, without touching it, and feel for any hot spots. If there are any, you will want to check what type of gasket you have. If it is mounted on the door, you will want get a professional to repair it. This type of oven repair can be very difficult. If it is on the oven frame, it is easier. You will want to find the proper type and size for your oven and buy it. Then you will need to remove the clamps holding the previous gasket and pull it out. Now clean the track it is in and begin to put the new one in. You do this by laying it in the track, at the top. Now press it in the track all the way around the frame and press it together at the bottom. This will secure the seal for your oven.
The other problem you could have that requires range and oven repairs is with the burner.
Many times the burners can be clogged with food particles. To fix this problem, you will want to shut off the power and/or gas to the oven. Now you can remove the burners that you are having issues with. Next just soak the burner in water with a cleaning solution. You can also use a needle or pin to clean out the ports. Avoid using toothpicks for this however. They could leave splinters in the port and result in more oven repairs down the road. Once you wipe the burner down and it dries, you can replace it in the oven.