If the TV does not have A/V inputs on the front or back and you do not use a VCR or cable box/satellite receiver in your system then you have no choice but to have this repaired. Expect this to be a standard repair service rather than minor. In some cases it could be major but the key is to keep the RF connector in case the service center can reuse it in repairing your problem.
If you do have a VCR or cable/satellite receiver in this system and A/V jacks there is a simple $10-15 solution, do not use the antenna input. For this you need simply connect one of those sources to the TV using the A/V output jacks on the source connected to the A/V input jacks on the TV. On your remote or TV will be a video or input switch which you must push to switch the TV to the A/V input jacks. If you have more than one input then pressing it repeatedly will toggle you through them. If you were tuning your channels directly with the TV tuner then the VCR is a great and inexpensive fix but you will change channels with the VCR remote and volume with the TV remote just like having a cable or satellite box.
Don't be surprised to find a slight to significant improvement in your video and a huge improvement in audio. The RF connector on your TV only has performance value if you are acutally chaning channels using the TV tuner. All applications of setting your TV for one channel while the box does the work degrades the signals and even reduces the audio to mono only. You can only get stereo audio using the analog audio or digital audio outputs on the back of the box.