Temperature seems ok, it's just the noise of the stock HSF that bugs, so I think I can get by replacing just the fan.
Does this seem like a sane course?
Do you mean something like this
but on an AMD cooler?
Should be possible with a little bit of modding and reasonable enough for a low power CPU like yours.
From memory, the AMD fan on their heatsinks is 70mm, so you might be able to buy a 70mm to 80mm fan adapter like this
and use a 80mm fan of your choice on the cooler. No guarantees that this adapter would work with your cooler though.
As for fans for this adapter, the Nexus Real Silent 80mm case fan would be one option. The Noctua NF-R8 fan might be another choice, and it comes with speed adapters to allow you to slow down the fan speed to certain levels. The Scythe Kama Flex 80mm fan and the Scythe S-Flex 80mm fan are also other options.
Alternatively, you could do a bit of modding and try strapping a 120mm fan to the heatsink somehow. This might require a bit of ingenuity in securing the fan to the heatsink. As noted in the caption to one of the pictures in the linked article, some wire ties from the struts of the fan might be necessary to secure it to the heatsink somehow, but the stock AMD heatsink doesn't have anything like that once you remove the fan and fan cover from memory.
A Nexus Real Silent 120mm fan (like the one used in the linked article) would be a pretty decent choice if you went down this path. Otherwise, a Scythe Slipstream or Scythe S-Flex 120mm fan would be good too.
You will also have to change your CPU fan speed control method to voltage in your BIOS to get the fan to vary with CPU temperature. Otherwise, you can just set it to a fixed speed that you find quiet using a Zalman Fanmate 2 or something similar.
Best of luck with this!