Federal Taxes: How Do I Fix My Amended Return

I received a form 8009-A from the IRS because we accidentally switched around two numbers in my son's social security number, so it is wrong.
My question is, can I just cross out the two numbers and write it correctly with a pen, or do we need to actually fix it on the computer and re print out the 1040x?
Also, I'm not sure where to send it back. The return address on the envelope that it came is "submission processing center/Fresno CA", is that where I send it back?

Federal Taxes: How Do I Fix My Amended Return