[joelhaus]

First off, congrats on getting this far! Regarding your questions...

1) Price tag - There are three approaches you should consider:

  a) Income - knowing the bottom line revenue 
  add should be very helpful. If they are a public 
  company, you should also be able to determine 
  their weighted average cost of capital (if not 
  public, you could try estimating it). Using these 
  two figures, you should be able to come up with a 
  fairly solid price using DCFs.

  b) Replacement - what would it cost them 
  (time + money) to build this from scratch?

  c) Comparable - is your product unique or do 
  they have the possibility of shopping around 
  for a competitor at a lower price.

2) Legal requirements - Find an attorney that specializes in contract law and IP. If you can't afford one, you might be able to find someone willing to work on contingency.

3) Other considerations - see #2 above and do this before anything else. Grellas, a contributor on here, probably isn't a bad place to start. It also wouldn't be a bad idea to have a fall-back plan if the deal falls apart; you'll alleviate a lot of the pressure during negotiations.

Good luck!