Installing or upgrading the various Intel wireless adapters by end users is not supported by Intel. There are many reasons for this. I recommend that you review the information at http://www.intel.com/support/wireless/wlan/sb/CS-031167.htm and http://www.intel.com/support/wireless/wlan/sb/cs-006006.htm. You should contact Dell or go to a Dell reseller like Best Buy for assistance.
Hopefully I can help answer these questions for you.
1. You need to go to Dell to determine whether your system is wireless ready. Even if you have a slot if there are no antennas in your system it won't work.
2. The suffix for the card does refer to the regulatory region. MW = Most of World and can be used in the US. RW = Rest of World and varies as to which regions it will work in but does not usually include the US.
3. Software is available at your OEM in this case Dell or at the Intel support site for downloads - www.downloadcenter.intel.com. You can use the Windows software utility to manage your wireless in most cases. The Intel software utility offers extended functionality especially for business users.
4. You should setup security on your router and wireless adapter. Check with Netgear on what security is supported for your router.
Keep in mind that installing a wireless adapter is not supported due to regulatory requirements and the OEM may prevent you from using an adapter you install yourself.
Intel Customer Support