Great idea and thanks for the legwork! I'll try to contribute
N52 problems:
- Valve cover gasket leaking/valve cover cracking. Symptoms: oil all around valve cover, spark plug threads oily,
- Waterpump + thermostat
- Oil Filter Housing Gasket
- (Not sure if this is still a thing but earlier N52s experienced it) Hydraulic valve lifter tick
If you're planning on DIY, I'd recommend these tools (on top of normal tools you need to work on any other car [metric socket set, jack stands, breaker bars, etc.]):
- 3/8" metric hex bit set
- 3/8" Male & female torx set (maybe with a decent bunch of 1/4" stuff for those tough to reach bolts, like the oil filter housing under the manifold)
- Flexible 1/4" and 3/8" extensions
- Just a million extensions of all shapes and sizes (1/4", 3/8", long & short)
- Universal joint socket connectors
- BMW jack stand adapters (or just cut some wood to stuff into the jack points)
- Quality torque wrench
- Metric offset box wrench set
Air tools are fantastic too, my impact gets used quite a bit. Also an electric screwdriver (you'll thank me the first time you remove the engine/trans skid plate LOL)
128i maintenance req's:
- Engine oil: ~6-7qts of BMW LL-01 Oil (honorable mention: Castrol 0w-40 euro blend)
- Oil filter: Mann-Filter HU 816 X
- Manual transmission: 2qts of GL-4 fluid (honorable mentions: Redline MTL, Redline D6 ATF)
- Differential (manual trans) 1qt of GL-5 75w-90 fluid (honorable mention: Redline 75w90)
- Spark plugs: NGK LZFR6AP11GS, NGK 6619 LFR6AIX-11
- Air filter: Mann Filter C 27 114
- Cabin air filter: Mann-Filter CUK 8430
- Power steering fluid (CHECK YOUR RESEVOIR CAP) but most likely 1 liter of Pentosin CHF-11S
- DOT4 brake fluid
- Coolant: 1gal BMW coolant + 1gal distilled water, mixed 50/50