I have a 2004 BMW 525,my question is how do you reset the oil change sevice light

You can find the oil life monitor reset procedure here
Oil Change Light Reset BMW 330xi 2001 2002 2003 2004 2005 Reset Your Oil...

IT DOES SOUND LIKE KEY FOB DYING AND I HOPE IT IS AS IT WOULD BE CHEAPEST PROBLEM TO SOLVE. GOOD LUCK

No you dont need to reset anything,you replaced the headgasket,what is the warning light that you are getting.

BMW Model E39 built from 1996~2000 will have a port like the one shown below. A Reset tool like a Peake R5 or R5-FCX is needed to reset the oil service or inspection service lights after required service.

1) If you have a reset tool then turn your car key to Position II but do not start the car.
2) Turn the cap counter clock wise on the Data Link Connector and insert the Reset Tool
3) Follow the instructions of your reset tool, different models may have different functions however they all create a short in PIN 7 to PIN 19 for a given amount of time.

OIL Service Reset requires pin 7 and 19 to be closed for 3+ seconds

INSPECTION Service Reset requires pin 7 and 19 to be closed for 10+ seconds

4) Once done, remove the reset tool and close the cap .
5) Your dash should light up with green lights at this point.
If the light did NOT reset after the above steps then you might be resetting Oil Service however an Inspection Service is needed.

Can you discribe the warning light please. Thanks

its not a big job just make anote how u take the old one out but yoy will need to take it to a garage to get them set up

WHat I found is that there are two gaskets, one to seal the cap and one internally.. BMW sells the filter and O rings in a kit, which cost $13.00.

This fixed the problem.

BMW requires a scan tool to reset the light.

Hi aajabbar , this can be tricky if you haven't reset the cbs indicator before
first turn the ignition on so that you have all the ignition lights on and the engine not running, once the service indicator has cleared fom the display, press and hold the tripometer in until the display shows a triangle then the microfilter symbol, release the button then press and hold again untill reset shows, then release and press and hold again untill you have a sequence of lines on display, once this has happened release the button and turn off the ignition, once the ignition is switched on again the sevice indicator should have reset. you may wish to print these instructions and familiarise yourself with them before carrying out a reset. regards Mark.

Im not sure which BMW your drving, but i belive in E46 3-series, you cycle the BC button till the temp is displayed, the click the trip button on the right side of the insurment cluster