I went in 2019, we had seats in the grand stand right across from Rossi's garage, it was awesome.
A few things I can share:
1. The track is near Florence, but in reality kind of in middle of nowhere, with no real transportation options to get there unless you have your own car. The train only goes to a neighboring town, not Scarperia. We made arrangements for a private driver to take our group of 6 to and from Florence, $300 I think. We made these arrangements last minute, so we had to take a ride at 5am and 5pm coming back. If I had to do it again, I'd look at renting a car for the day. Having a car in Florence is a disaster though, not needed at all, and nowhere to park it.
2. The track motto is Non Si Dorme which means something like We don't Sleep. There is also camping at the track, people party literally all night. We showed up on Race Day at around 6am and the party was still going with their chainsaw engines and air raid sirens blaring. Empty beer everywhere. It was an epic scene.
3. The main grandstand is one of the few areas with shade. Mugello is usually in July, it can get pretty warm otherwise. I was glad we had shade and seats, but general admission would be good as well.
4. We flew SFO to Rome, you can find lots of trains to get you up to Florence/Tuscany area. Florence is an amazing town to visit.