I realize my reply is a bit late, so please excuse me. To rip out unwanted material from DVDs such as trailers, warnings, etc, I use DvDremake. It's a simple to use program and fast. Simply view the blocks and menus that make up the VOB files and remove as necessary, then export the project. If after removing the unwanted material your project is still too large, then use DvDshrink, and the results will be better than having to compress/reencode the entire DvD.
Here's a link to what the pro version can do, but honestly I'm happy with the regular version.
http://www.dimadsoft.com/dvdremakepro/index.php