Southwest Airlines currently only operate Boeing 737 airplanes. There are several different versions of this airplane though, so the seat count can vary.
The answer depends on southwest of WHAT and since you have not bothered to provide that crucial bit of information, it is not possible to give a more useful answer.
The plane's seats...
Depends on what kind of plane you take. I have been on planes that have as few as 6 seats, and as many as 300.
Southwest is adding wifi to more planes all the time. They don't expect to have wifi on all flights until 2012.
Boeing
737
No, Southwest does not allow dogs on their planes, unless you have special needs.
planes
Yes, some planes have over 200 seats.
none of the above.
The time I sat in that row, the seats did not recline. They were uncomfortable. I try not to sit in them.
Many different planes fly from East Midlands Airport all with different seating arrangements.