Extending post.php, expanding the DB?

I want to hack wordpress so that I can include some extra fields on the post page. Essentially I’d like to do music reviews, and have seperate fields for Artist, Title, Year of Release, etc. plus Tracklist and ability to upload a cover (tricky?). I’m wondering if it makes more sense to copy post.php to review.php (for example) and hack that, or whether it’s fine enough to rip into post.php and do a little drop-down like the Advanced Controls to make the extra options hidden if they aren’t to be used.

I’m thinking a second file would be best, as any updates made to wordpress would lead to one massive headache to update with my changes, which are sure to be somewhat extensive.

My php knowledge is also quite basic, so this introduces some trouble ?? any suggestions on how to proceed and what else I might need to do would be very appreciated. Thanks.