1st try setting your linksys to UPnP setting. If that doesn't work, then follow the instructions as suggested, also changing your LW advanced firewall settings to manual port forward & using the same port as you set for the router.

No it won't affect WAN access. Your router is for external internet access. Internal wan or lan settings are independent of this. Unless of course, you're trying to connect more than one LimeWire thu the same router.