Don't change any settings on the router in the house (assuming everything this is working correctly).   Connect your ethernet cable that goes to the shop into a LAN port on the house router and also the shop router.  In the shop router settings disable DHCP and set your wireless network up to your liking.  I'd recommend the exact settings as the house network EXCEPT make sure it is using a different wireless channel.  Use channel 1 inthe house and channel 6 in the shop.