Solid Hardwood, Engineered and Laminate Flooring - cork under 3/4 hardwood?

I'm installing 3/4" oak hardwood flooring for the first time. the subfloor is 3/4" t&g with 1/2 plywood on top. It is a small section of our bedroom (about 75 square feet). I have a couple of questions.

1) the area is over a crawl space with an unfinished ground. There is however plastic sheeting on the ground as well as 19R fiberglass (paper down) between the joists. Is it advisable to use plastic again when laying the flooring down?

2) what fastening method is better. nails or stapled?

3) is it nessesary (or are there any benefits) to use a cork underlayment or would #15 felt paper be just as good. (is there any concern in nailing through a cork underlayment?)

thanks for any help you could give
deacon

Crawl space should be dry and covered with 8 mil minimum polyethylene, overlapped, taped, and run up the inside of the foundation and taped. This acts as a vapor retarder and keeps moisture emissions from rising through the subfloor. Vapor retarder on fiberglass batts (facing) is placed toward the heated space.

An additional vapor retarder is installed over the subfloor (plywood or OSB acceptable) for installation of hardwood. 15# minimum roofing felt is recommended.

Flooring cleats are recommended for installation of solid 3/4" haradwood flooring. The first row is typically drilled and face nailed with finishing nails. The next two rows are drilled and blind nailed in the tongue. Then, you are ready to roll with the flooring nailer.

Hardwood flooring should acclimate in the rooms where it is to be installed for several days in order to adjust to temperature and humidity. A moisture test should be done. There should be no greater than 4% difference between subfloor and hardwood flooring moisture content for 2 1/4" strip flooring and no greater than 2% for wider plank flooring. Continue to acclimate until recommended difference is met.

For additional info on solid hardwood flooring installation, go to the National Oak Flooring Manufacturer's website at www.nofma.org. Click publications and download for free the NOFMA technical manual on hardwood flooring installation.

thanks twelve, i'll make the recommended changes.