Ah, the yearly iPad update ritual has taken place at the 2801's...Pop gets the new model, Ma gets last year's, and the Office Manger is getting the 1 as a bonus....
I've noticed that if you get the new one and use the 'I am an existing iPad account holder', it takes the balance of your existing 3g account and converts the balance of it to LTE without incurring anything extra. It also gives you an option to go to 3 gigs of data for $30 a month once your current month expires. Nice.
When I go to the old iPad, it appears to give you a fresh sign up screen as well.
I'm unsure if it's possible to put the sim chip in a computer, hack it, and retrieve the cc info. I don't believe it is, but I cannot say so with certainty. I also have gotten replacement sims from AT&T in the past, and I believe I can obtain an iPad 1 sim from them, but again, I cannot say so absolutely.
Maybe Apple or AT&T has the answers your looking for, instead of my guesses and conjecture. Good luck!