Got a letter from the IRS re: I owe more money from 2012 - need help from abroad

I received a letter this week from the IRS stating that I owe an additional $1,500 on my 2012 taxes. After looking at the documents, I definitely screwed a few things up on my tax return that I would like to fix, but I am currently deployed for the next 4 months and I don't have access to a CPA or anyone who can help me with this.

My errors are:

1 short-term capital gains (mutual fund sale)
2 long-term capital gains (1 mutual fund, 1 stock)
2 missing W-2 forms from jobs my wife had prior to our marriage. Both of the businesses are now closed and the total taxable wages for those jobs is $1,339.

Since I did not report the sales of my mutual fund and stock, they are wanting to tax the entire amount, which is wrong because I should just owe it on the gain, correct?

I have the 1099-B for these sales and I have determined the cost basis and I have the total gain, but I am having some trouble figuring out how to put all of this onto a 1040x.

If anyone can just point me in the right direction I would greatly appreciate it. I have a general understanding of how it all works but I am just lost on a few of the details.

Also, is it possible for me to get an extension since I am currently deployed? I would feel a lot more comfortable if I could take all my paperwork to someone to look over this when I get back.