Hi there My name isXXXXX will do whatever I can to help you. Please be sure to ask me of anything you are unsure about.
I agree totally with Aric.
One thing to note though, is usually when you re-tune, somewhere at the beginning it will show signal strength and signal quality. Make sure these are satisfactory before proceeding. If not, then it may be that the cable (most likely co-axial) is a bit iffy and needs replacing, or it may even be the aerial needing re-aligned, which you will need a local engineer to do for you.
Hope any or all of this helps, and be sure to keep asking questions until you are satisfied. :)