When you say its not working, has the function disappeared in the cluster?
Unless the engine has an empty/blanked off dipstick hole then the only way to check the oil level will be to get the cluster function operating again.
You could I suppose you could drain the oil from the sump measure the amount that was in it add the correct amount and put it back in but this is really quite impractical.
The buttons on the steering wheel are not working. I have been informed by two independents that it is either the buttons or a ring in the steering wheel that picks up the signal. It has frozen on settings, so nothing changes to the display on turning on the ignition or whilst driving. Bloody annoying as I can't change anything.
Ideally, you should check the oil level when the engine oil is cold. If you have to check after you've been driving, whilst the engine oil is warm, then wait 5 or 10 minutes for the oil to drink back down the bottom of the engine.
To do it from the cluster you'll need to wait for a few minutes, as the car will refuse to take a measurement until it's ready!