Answer to 1): I think it will be about the sticker difference, which is what, 14 MPG?
2) at 15,000 miles per year, the EX would cost (at $2 a gallon) $936 for the year and the HCH would cost you $625 per year, a savings of $311 per year.
3) cost for maintaining would be virutally identical - the IMA checks are included as a regular part of service trips.
4) The Hybrid is likely to hold it's value a little better, as in the history of US autos, any car in the same line which is "higher cost" holds that resale difference the entire lives of the cars. In other words, a 2002 Civic DX and a 2002 Civic EX will maintain a comparable resale difference in relation to their "new" price. Same should hold true with the Hybrids. Go to kbb.com and get Blue Book values on a 2003 Hybrid with 30,000 miles and a comparable 2003 EX with 30,000 miles and you will see what I mean....

Good Luck Shopping !!!

P.S. if you can wait about 4 months, the 're-designed' 2006 Civics will be available, more power and better MPG in the HCH than the current version.