Yes, you can do that. You do need to understand IP networking to configure the networks properly on the machines to make it work right.
Question is why? I assume your LAN1 connections go to a switch (probably a single switch). Unless something is overloaded or you're already putting heavy load on the the LAN1 connection, you're not going to see any noticeable change speed changes using your LAN2 cross-over cable idea.
Thanks. I'm just wondering if there will be a significant improvement in file transfer/sharing speed..but maybe not ...just like you said there will be no significant improvement even when connecting straight instead of going around a server.