Check with a Retailer or Installer to see if you should glue directly to a FINISHED surface. Your current hardwood has a poly on it (I assume.) I'm not a Chemist but there may be a 'reaction' between the glue and the existing finish on your hardwood floor.
Have you considered refinishing the floor? You may find it costs the same to install a laminate floor, even if you did the install yourself. You'll need to find out if there's enough flooring left to refinish. Have a Pro stop in and give you an estimate. At the same time, ask him how he knows the floor can be refinished. He'll show you the 'tricks'.
Check out the glue-finish 'thing' if you're taking your original path. My best to ya and hope this helps.