You are welcome. This is pretty straight forward. I will answer your questions as you posed them:
1. Print this out and send it to the ex.
Yes, Make sure you fill in the bank for the exact action that she is authorizing you to take on her behalf. It may help if you take this form to the bank and see if they will tell you what you should put in the blank for the action to take.
2. The ex signs it with a witness and notary.
Yes, a witness and a notary where she is located.
3. The ex sends it back.
Yes, she must send the original back. A faxed copy or scanned copy is not sufficient.
4. Do I need to sign it as well, with a witness and notary?
No, you do not need to sign anything. You will present the original signed power of attorney, along with the check to the bank and sign the check with your name and with her name as "attorney in fact" for your ex.
5. Then I take all the signed documents and check to the bank?
Yes, see above.
There is certainly no harm in trying these steps on your own. If you do not have luck or it is too confusing then it just may not be something you can do on your own. You should then get an attorney experienced in trusts and estates to help you with this transaction.