The radio in my 88' 300e has gone out, I think it is only the on off switch. Any chance at repair?

I really would just as soon change the radio to a unit with cd player. I called circuit city and talked to the installer
which brings me to ask the following questions:

Will the ant. still go up 1/2 way when the radio is turned on? and will the dash ant. switch still function as always?

Does this car have an amp?

Are the speakers common ground?

Any issues I should know about?
Thanks in advance guys.

cgar