If I sent off my amendment but forgot to sign, will the process start over or pick up where left off after signing?

[Mike9241]

The IRs will either send back the return for signature or a substitute form that will satisfy the signature requirement. Be sure to send it back ASAP . 

[DoninGA]

If you mailed a prior year amended tax return without signing the amended return the IRS will mail the amended return back to you for a signature.  Once signed you have to mail back the amended return and that starts the process at the IRS anew.