A payment of $452 was made on my federal tax return. I had amended that last month and mailed it, and it showed that I was now due a refund of $428. Do I get reimbursed?

If you owe less tax as the result of filing an amended return, the IRS will refund the money as soon as they have processed the return and verified that you are entitled to a refund. It takes them a while to complete that process, especially at this time of year when they're really busy. You should probably allow about 2 months for them to get the refund to you. If you want to verify that they've received your amended return, you can always call them.