If I used TurboTax for MO amendment and paid what was due. Told me to mail my amendment in however it only provided a payment voucher, do I need to mail anything else?

It depends.

If you electronically filed your amended tax return and chose to have the payment directly taken from your bank account, then you will not need to do anything with the payment voucher.

If however, you chose to mail your payment in, you will need to mail a check with the payment voucher.  Be sure to list the tax year and form that the payment applies to.  Missouri also offers the option to pay online.  See this link for more details.