If you really wanna go all out for the 100k refresher....

OSV Vavle (oil seperator, PCV, whatever) and the flush/replace the hoses going to it since they clog - can freeze over in the winter causing all kinds of issues, also causes the infamous blue smoke at start up
Valley pan gaskets - Since you've got the intake off. If you're looking for a great and cheap mod, search your local junkyards and get a pre-VANOS intake manifold, then get some $$Dinan$$ or Powerchips software to make it work better.
Waterpump - They're usually fine, but bearings can go out at any time. Find the composite one per 'killcrap' suggestion since he says the metal blades tend to bend under the fluid pressure
Verify the heater diverter valve is working properly and aux pump (one unit) - confirm the plungers inside move up and down, they control the driver/pass side heaters. The aux pump assist w/ flow, you'll hear it
Radiator hoses - preventative maintenance
Radiator - necks get hairline cracks
Coolant - duh Zerex G05 is phosphate free and cheaper than the BMW stuff by a few bucks
Expansion tank - they just burst sometimes
Thermostat - I've had two fail on me, one original and one BMW dealership replacement...it sucks.
Spark plugs - NGK Iridiums from your local, reputable auto parts store for $8 vs the dealership ones for $25
Drain and fill transmission - Valvoline Max-Life is compatible w/ Esso for 1/5th the cost. Techniques can be found on www.e38.org since the trans need to be at a certain temp for this procedure Also follow that site for links on proper bleeding techniques of the cooling system, that's VERY important.
Drain and fill diff and transfer case - Redline fluids
Fuel Filter - just because
Brake Fluid - just because
Check the power steering fluid color - always overlooked and an easy job using ATF

This is all I can think off of the top of my head. I get a lot of stuff off www.autohausaz.com. Search for some of Weasels threads, he posted a cheap place for the radiator. Also find an Inspection I and II checklist and go over some of those things as well.

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