^^^ Almost correct. Anonymungus! is 100% correct insofar as you do want to get the levels as consistent as possible via automation, then apply compression for the final touch.
The problem is that volume envelopes are post-fx, so wildly-varying levels are just going to confuse a compressor and potentially make things worse.
What you need to automate is not volume, but gain. Unfortunately, SONAR does not support gain automation. However, you can easily achieve this using a gain plugin. Blue Cat Audio offers a free one in its
Gain Suite. You'll most likely want to use the mono version, as I assume the recording is not stereo.
If there are sections where the audio is actually clipped from people speaking too loudly into the microphone, then some sophisticated restoration software will be needed, and even that will likely only be partially successful.