Yes, your administrator can see that you've unenrolled if you haven't used fakemurk or murkmod. More specifically - your network administrator will be able to see that the "Last Sync Date" on your Chromebook will be slowly drifting into the past. However, there is no indicator saying, "This device is not enrolled".

Short answer: No. Slightly longer answer: Not unless you mess up really, really badly. Basically, just follow the instructions and you'll be fine.

Use a recovery drive. If ChromeOS refuses to load it, check that you got the right board on Chrome100. If that doesn't work, make sure that this screen isn't intentional, as it is in fakemurk.