what i think he meant by customizing is that everything has been done...so it isnt customizing anymore....it is called copying. sure some stuff hasnt been done but it is going to cost a lot of money to be "diffrent". and that isnt why you bought a civic in the first place. i would say...screw the interior...keep it factory clean. i really do laugh at people with white interior pieces or yellow....or red....etc... black is good!!!!
as for books....i would pick up a copy of honmda acure enthusiats. shoudl be at any book store. it is a great book to teach you te basics. it isnt a how to but more of an idea starter.
keep it clean and simple....you will thank me when your done.