Detailing and polishing paint? Yes. Cleaning an interior? No. As long as it isn't already battered and old, some good quality interior wipes, glass cleaner, and a trip to the car wash to use the vaccuum will get the same results.
Never seen any aftermarket deck that looks "cheap" looking, but to each his own
Look in the other thread about the guy that replaced his double din with a cool Pioneer unit. I know the front on yours is different, but it shouldn't be too hard to find a double din one, even in good condition. They add A LOT of functionality; plus, who listens to, or even makes cassette tapes any more?