I've only done one of these, that was HIGHLY bonused by a scheduler who called me directly. It took me about an hour onsite, but the location was very slow making it go relatively fast... Up until the very end where I spent 15-20 minutes waiting for the manager to break away from a customer to sign the form at the end of the audit.
Although I read through the paperwork first, I feel like it was kind of hard to comprehend it all until you're actually doing it, so your first will go slower, but subsequent ones should go faster. The manager will probably want to schedule during a slow time anyways, but you should be aware to aim for that as well just in case. During the day time on a weekday will go much faster than an evening or weekend.
Are there two different types of audits? Or is it based on the type of location? Most stores around me seem to start at $25, but there are a couple locations (at least one is in a mall) that start at $14. I wasn't sure what exactly caused the difference.
The reporting isn't horrible, except this msc's site has SOOO many different pages that you really need to make sure you've got a good, fast internet connection or you could eat up a lot of time just waiting for the pages to load.