You will be doing an Inspection I service. Sorry, I don't have any idea of cost, I do this work myself. The following is a cut/paste from the Service Information for a 2006 USA Z4. I've included all service levels for convenience. The formatting got lost, but it should be readable.
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Engine Oil Service
Engine Compartment
Change oil and oil filter while engine is at normal operating temperature. We
recommend BMW 5W-30 High Performance Synthetic Oil, p/n 07 51 0 017 866.
Reset service interval indicator.
Replace microfilter.
Check overall thickness of front and rear disc brake pads using special tool. If
replacement is necessary: Examine brake disc surfaces. Clean brake pad contact points
in calipers. Grease wheel centering hubs. Check thickness of parking brake linings only
when replacing rear pads
Check parking brake actuation. Adjust if necessary.
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Inspection I
Only those items of inspection work which apply to your vehicle will be performed. This list is subject to
amendment.
Undercarriage
Change oil and oil filter while engine is at normal operating temperature. We
recommend BMW 5W-30 High Performance Synthetic Oil, p/n 07 51 0 017 866.
Check transmission for leaks.
Check rear axle for leaks.
Half-shafts: Check for leaks at flexible boots.
Visually check fuel tank, lines and connections for leaks.
Check condition, position, and mounting of exhaust system. Examine for leaks.
Check steering for absence of play, condition of suspension track rods, front axle
joints, steering linkage and joint disc.
Check overall thickness of front and rear disc brake pads using special tool. If
replacement is necessary: Examine brake disc surfaces. Clean brake pad contact
points in calipers. Grease wheel centering hubs. Check thickness of parking brake
linings only when replacing rear brake pads. Check brake system connections and
lines for leaks, damage and incorrect positioning.
Check parking brake actuation. Adjust if necessary.
Check all tire pressures. Correct if necessary. Check condition of tires (outer
surface [left/right]), tread wear and pattern; in case of uneven tread wear, readjust
wheel alignment if requested (invoice separately).
Inspect entire body according to terms of rust performation limited warranty. (Must
be performed at least every two years).
Engine Compartment
Read out diagnostic system.
Check engine cooling system/heater hose connections for leaks. Check coolant
level and antifreeze protection level. Add coolant if required.
Check windshield washer fluid level and antifreeze protection. Fill up and/or
correct if required.
Check air conditioner for operation.
Replace microfilter (Note: reduce replacement interval in dusty operating
conditions).
Reset service interval indicator.
Check brake fluid level. Add fluid if needed
Body/Electrical
Check battery state-of-charge indicator and charge if required.
Check lighting system, i.e.: headlights, foglights, parking, back-up, license plate,
interior (including map reading lights), glove box, flashlight, illuminated makeup
mirrors, luggage compartment lights.
Check instrument panel and dashboard illumination.
Check all warning/indicator lights, check control.
Check turn signals, hazard warning flashers, brake lights, horns, headlight dimmer
and flasher switch
Check wipers and washer system(s); wiper blades, washer jet positions.
Check condition and function of safety belts.
Visually examine all SRS airbag units for torn covers, obvious damage or
attachment of decals, decorations or accessories.
Check central locking/double lock.
Check operation of all latches.
Check heater/air conditioner blower, rear window defogger.
Check rear view mirrors.
Final Inspection
Road test with check of brakes, suspension, steering, clutch/manual transmission
or automatic transmission.
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Inspection II
Includes all items listed under Inspection I, and the following checks and maintenance operations.
Engine Compartment
Replace air cleaner element. (Note: Reduce replacement interval in dusty
operating conditions).
Brake Fluid Service
Replace brake fluid every 2 years (time interval begins from the vehicle’s production
date).
Oxygen Sensor Service
Replace Oxygen Sensor every 120,000 miles.
Spark Plug Service
Replace spark plugs every 100,000 miles.
Automatic Transmission Service
Replace ATF every 100,000 miles.