Hi Baywatcher
iPad isn't a laptop so can only use app store apps, I think Firefox is not one of those. (There is an iPhone version however but if it is flash you need then I think you may be disappointed)
By setting up airport express do you mean that you carry an Airport express with you and plug it in to an ethernet cable in the hotel then want to configure it with the iPad?
If so, I am not sure unless you can use Safari to access the the settings on the airport express but not sure how you will go with authentication, I think it might depend on the system.
Good luck!
jetset