Thanks for asking some "right" questions - the whole experience is so intense that it is hard to know where to start...
I started planning to go there one year in advance - I looked for dates where there would be no events at the track set my heart on end of June/beginning of July.
I waited for January for the calendar to be published and moved on to book the ferry to Rostock. Due to the ferry schedules and the time to get from Rostock to Nurburg, this meant I would arrive to Rostock on Thursday ad 7AM and leave from Rostock on Tuesday at 16PM.
I booked a room in Adenau from Ringvilla for 5 nights, together with my friend that came from Portugal on his Megane RS (can be seen at the beginning of some videos)
The trip down from Rostock to Nurburg was very interesting - my first stretch of unlimited Autobahn served to find out how fast the Saab did go, which was 250 (GPS and limited). At that speed, it is like time travelling and after doing it for 1h30 or so, I realized that my full gas tank was almost gone, which was scary, but... I also realized that I had shave 200km out of my 700km trip down - it is a bit like a time travel.
- Altogether, cost wise, door-to-door, I spent about 1300-1500, all included. But I did not take a cabin on the ferry, which was a huge mistake, but would have also been €660 more to the whole price, unless you find others to split with.
- The car behaved surprisingly well on the Ring, understeering a bit only on the 1st lap because I still had the max tire pressure for the autobahn. I also studied the track in detail for one year and all the correct lines so, even though I had never driven it, I managed to get fairly good lines straight from the 1st lap.
The reason for not much gear changes is... that they are not needed

You can almost do the whole track in 3rd/4th gear with a brief bit on 5th. Otherwise, if you look at the 4th video, where the metrics were working, you can see from the RPM and gear that there was no need for gear changes, at least for the V6 engine, which has a lot of Torque.
There is
no video (mine included) that can prepare you for the track topography, cambers, height changes, sudden drops, tight and fast downhill turns, blind turns and the 3(!!!!) jumps that you HAVE to be aware of. That was my biggest surprise - I saw someone describe the thing as a rollercoaster ride and that is pretty much what it feels like.
- The fast vs slower cars... Well... I had Porsche GT3s and modified BMW M3 all over me the whole time, but it is usually ok, provided you keep in mind that it is not a race and you put the ego aside. I was more interested in not crashing than proving I am fast. The track is VERY dangerous and people die there all the time. Crashes are multiple per day and usually the track gets closed so... plan taking that into account.
As for slower cars, some people actually try to race you, defend lines and so on... errrr.... good for them!

I did not risk overtaking where I did not feel was safe, specially because you have to brake after overtaking and braking and turning such a heavy car is not so easy. Also, the track is quite tight/narrow, something that was not apparent from the videos.
On weekdays tracks usually opens only 1h to 1h30 and if someone crashes at the start of the session... that's it for the day!
- Tires and fuel? well... I did not 0 meters but I estimate anything between 20-25. You are pretty much on full boost the whole time.
By the end of the lap, you should go drive around Nurburg for a while to cool the car - when you slowdown at the track exit you will smell everything... engine, coolant, clutch, brakes...

...rubber.
- Road tires can do 1 lap, max 2 before they desintegrate. Also, at the end of the lap, my stock brakes start to be faded and not working anymore.
As mentioned, on Autobahn, I hit 250kmh but mostly cruised at 200 on the few unlimited sections. Otherwise, limits were 130, 120 or 80/50 in the (way too many...) construction/repair areas.
On the track, you will be hard pushed to reach 200 or go over, and only for short periods. The famous big straight has (a little know fact...) a 120kmh speed limit on Tourist days and the police is there checking speeds sometimes.
I am glad to answer any other questions and share links for sites and vids I used as reference for this trip.