If you are looking for a 2000 540 heres some things I learned with mine.
First I purchased a 2000 540ia fresh off a lease return with 50k on the clock.
I am a big mustang fan by the way you should'nt have gotten rid of the stead. I currently have a 2000 R model (#91/300) and a 85 GT anyways back to the Beemer.
58k-Replace serpintine belt
59k-Brakes front and rear/pads brembo cross drilled rotors,factory M5 wheels, bridgestone tires.
59.9k-Heres the surprise I had, I know the above items are all wear and tear issues so no big deal, but the transmition going out on a car that stickered for almost 60k at these miles????anyways the remaining FACTORY warranty saved me big$. The dealer replaced with a brand new trans at no charge.
65k- Radiator started leaking. I replaced with a factory one and at the same time decided to do the water pump, thermostat and fan clutch.
70k- performance big hit me, added Dinan cold air intake, MAF, M5 exhaust (drivers side only) removed resonator,Dinan stut tower brace, Stage 4 trans and engine software. These mods woke up this beast!
80k- navigation unit went out (this car has the MK11).
currently the car has 87k doesnt burn a drop of oil and feels better than most new cars out there, expecially for a 5 year old car. Hope this helps out.