As a follow up there is also a model train show next Saturday, Feb. 16, in Stafford which is also on the SW side.
North of Houston is Spring Crossing near old town spring - best in the Houston area by far if you want friendly help!
This shop here. Ace, the shop's owner is one of the nicest guys you will meet. He's also a wealth of information on HO/ N scale/ trains in general. He also has a few super detailing parts you don't find every day like Sunrise Enterprises.
Mikes hobby shop porter Tx 10 mins from IAH Drive towards Kingwood the road right in front of the tracks (494) then turn onto e. Knox drive (big sign for Knox farm and feed and you are there!