ACX Check will allow you to check the file yourself before uploading-submitting it. (It doesn’t check your MP3 bitrate.)
If you are using the current version of Audacity, Koz’ new Audiobook mastering macro will nail the peak & RMS requirements.
If you simply raise the volume to meet the RMS spec you’ll probably fail the peaks. The macro includes limiting which pushes-down the peaks (wiht minimal effect on the RMS level).
Note that any boost will also raise the noise floor so if you are “close” that may go out-of-spec. (Any regular-linear change in volume will change the peak, RMS, and noise floor levels by the same dB amount.)
In the Export window, after selecting MP3:
Bit Rate Mode = Constant.
Quality = 192kbps (or higher).