My question is, if I were to install the Leopard Server Packages on my main iMac, and really only mac, would it mess up other stuff? Like would some apps not work now? Would it function just the same as it does now, plus the server functionality? I don't want to install them unless I know for a fact that it will still be the same, just added functionality, such as a Open Directory server.

In some ways not really but I say go for it