I just tried to install pfsense but stuck at auto-detecting LAN interface. NIC cards have been detected correctly but unable to proceed with installation because my router is not set-up as 192.168.1.1 but 192.168.2.xx. I am not willing to change my IP addressing (too much work) setup just to try out pfsense. Am I stuck?
No, you're not stuck. The Auto detection function doesn't need a working IP subnet to be available for it to work; only that the link goes up on the port. You can simply connect any computer, switch or hub to that port via a cable to push the link up and it should work fine. Once that is done, immediately go in to set the interface addresses.
Basically, you will be setting LAN to 192.168.2.x. If your current router is 192.168.2.1, you might want to set the pFsense box to 192.168.2.2. Then head over to your current machines and add 192.168.2.2 as a 2nd gateway/ dns IP. Just remember that DHCP server should only be enabled on either router but not both.
What this does is to allow you to have both your current router and the pfsense box on the network at the same time and once the pfsense box is properly configured, you can simply power down the old router and the machines will automatically switch to the pfsense as the new gateway. In the event that the pfsense screws up, simply unplug it or power it down and switch over to the old router to restore network access.