BGM, if you take care of her she'll take car of you! These are fantastic vehicles. Sure I've had a number of repairs, but nothing too bad or overly out of the ordinary. And if you're able to do your own work it doesn't cost much. For a car like this, and no car payment, I couldn't be happier.
A few notes,
1. Change oil every 5k or less! Don't go by the 16k (absurd) recommended BMW interval.. Never use 'high milage' oil. It can destroy your seals. Always use recommended synthetic. I use Castrol Syntec 5w30.
2. If a plastic coolant part breaks, only use approved BMW coolant. Never the basic stuff. It's acidic and can cause premature breakdown of your plastic coolant parts.
3. Get your coolant changed at BMW if you have not already. They use a fluid with treatment during the flush that will breakdown and remove sediment in the system. This is very good as it protects the functionality of your heater core. If you wait you risk the core getting clogged and your cabin heat failing. You don't want this if you live in cold areas. And it could cost $6k to fix / replace the core. A ~$100 flush at BMW is very worth it!
4. p0012 and p0015 are typically Vanos related. It's easy to resolve. I'll link below. Usually it's just a cleaning required. Top Vanos is intake (p0012) and the bottom is exhaust (p0015).
https://www.youtube.com/watch?v=zOdPvvOVqsI
5. p0420 and p0430 are the infamous cat codes of death. You don't want to have to change your catalytic converters on a BMW. I was quoted $3200. You can use the following to fix this for $5 - $10. And your vehicle will still pass emissions. I didn't see a reduction of gas mileage after doing this. The first link shows you how to remove the 02 sensors. You'll then install the spacers also linked below and reinstall the 02 sensors. Poof, codes are gone!
Removal:
https://xoutpost.com/bmw-sav-forums/...-post-cat.html
Spacers:
https://www.amazon.com/gp/product/B07H2DNRNZ/
6. The spark coils go on these from time to time. They're about $45 each at Auto Zone but you could preemptively purchase a pack of 6 on Amazon and keep them with you. You notice jerking acceleration / misfire when one fails. The codes are P0301 (Front / Radiator) - P0306 (Back / Firewall). Simply remove the decorative cover over your head. Each coil has a connector with a pull up clip. Unlatch the clip and pull the coil out. It could take 5 minutes and will spare you a tow or very troublesome drive. Personally, I would replace them all now and keep a few in the car for later just in case. A small tool kit including a set of allen keys is a good idea.
7. At 100k it's a very good idea to look into getting your Transmission fluid changed. This should prolong the life of the transmission. You may also consider replacing the fluid in your transfer case. If you wait the transmission could fail early. Or, if you change the fluid later it may start slipping or be unusable.
Just a few thoughts. I hope it helps your beast from turning to dust!