Sorting the search results probably wouldn't be too bad on the database, but it would likely require us to modify the vBulletin source code a bit which we are trying to stay away from doing.

As for setting the 3 character search limit... Yams is right, although vB's current method of using an external search table is old. Mysql has a built-in fulltext index that we should be using instead (unfortunately, vBulletin 3.5 needs to come out first) but even that limits words to 4 charaters or more.