Oxygen sensors

[blue thunder]

I just have a few general questions. While holding steady around 40 mph the throttle sound changes in and out. The speed stays the same just fine. I checked my engine codes and I am getting 32 and 37. Both oxygen sensors. The cheapest I found is around 100.00 each. Do I have to replace them to get the engine running smoothly again. I am going to try a throttle body cleaning as well. I am strapped for cash at the moment. Just wanted more info on this matter. Thanks.

Mike