Yes, if filing an amended return lowers your tax liability, you will get a refund. And yes, you will need to mail a copy of any new forms you enter. The program will advise you what you need to mail when you finish.
OK. Instructions should be specific. I am done, and my instructions just say to send what changed--and gave me a huge packet including my prior 1040 with the K-1 information entered. It says nothing about sending (or not) original documents.
The forms that printed with your amended return should be everything that you need to send. When you enter a K-1, it is not unusual that many forms in your original return may have been changed since all the information from the K-1 is transferred to other forms. That could explain the reason for the large packet of forms.
You do not necessarily have to send a copy of the K-1 with your amended return, but it does not hurt. Look closely at the packet of information that printed and you may find that there is already a K-1 being included. Either way, be sure to keep your original document with your records.