It's not as bad as it sounds.
You just need to remove the plastic surround and it is 4 torx screws to unbolt the head-unit.
Start with the top mounted air-vent and work downwards. Here's a good link to follow:-
It shouldn't take you more than about 5-10 mins.
I also suspect it is the aerial not connected properly or even the incorrect cable is connected.
Let us know how you get on. There is no need to take it to a garage. You should be able to get enough help from the forum to assist you.
Good luck!