RE: Speakers
I've replaced rear deck speakers on a 91' Continental before which was pretty easy since the grille just pulled off. I've never done it on a TC though.
Be careful with what speakers you replace them with. If you get some nicer speakers, the stock amp won't be able to power them and you won't have any bass. I'm not sure what stock amps usually put out, but it's probably something like 15 or so watts rms (if I had to guess.)