This site has an extensive database - go to the top blue toolbar, hit 'database' and select Missouri from the state map, or the pulldowns. Go to our Missouri forum and ask away. You may also find additional users, and freqs not in the database in the following Yahoo group...
http://groups.yahoo.com/group/StLASE/
We also have a very extensive wiki section with articles on all the major trunktracking radios (many areas have switched to this...), trunking in general, links to FAQs for beginners and a great deal more. In that same top blue toobar, just hit the 'wiki' link and away you go.
Lots has changed in a few years - take the time to do some research before plunking any money down.
73s Mike
[edit] I forgot to mention this - on both this site, and the wiki, anything printed in blue is a link - even if it appears to be a word. Clicking on it usually will send you somewhere.