Mr. White is correct. You'd have to supply a lot more info to get an adequate answer. It may not just be a single antenna that will be needed to cover the motel. Depending on the layout, you might actually need several APs, specialized antennae or "leaky" cable, etc.
A couple of suggestions:
1) Contact someone in your area for an estimate of the job. In fact, get several. That might tell you if it is even something that is possible to do yourself, or you are in over your head.
2) Get rid of the NetGear unit, and get something like an ORiNOCO AP-2000. The NetGear won't handle the traffic very well if you get more than a few users on at the same time; which is kind of the whole idea of a motel setup.
3) The final consideration is bandwidth. What kind of pipe is going to feed this setup? It will need to be a business class DSL (ok) or a T1 (better) if you expect to get very many users.
If you are going to provide this service to your customers you'll want to do it right. Especially if you are charge a surcharge like is done for telephones. Otherwise is will cause a fair amount of grief. Do it right and it can be a money maker for you.
Stop the TSA now! Boycott the airlines.