If I want to apply for filing my taxes, what is the form I require to fill.

Also I am planning to apply my taxes and apply for my wife tax Id number.

If I file for extension, Do can I file for my wife tax ID later when I file taxes?

What is the new deadline

If you want to file joint return, you will attach W-7 (ITIN application) with your tax return. If you do not attach W-7, IRS will process it as married filing separately.
File for extension. Pay the tax due. File when you are ready with W-7 but before Oct 15, 2010.