Nissan Repair: p0300 code 2003 nissan altima 2.5s, blown head gasket, 2003 nissan altima

Question
My car had just gotten a head job due to a blown head gasket and  now the "service engine soon" and "ABS" and "Airbag" lights are lit on the dash.I noticed some smoke upon start up and a very rough idle and decided to do a computer scan and it turns out theres a code p0300.It seems that oil is finding its way into cylinders #1 and #4 after checking the spark plugs even though all are giving signs of correct compresion. My questions are: (1)Is there anyway of repairing this problem or is a new engine the only solution.
(2) Does having worn brake pads cause the "ABS" light to come on and lastly why is the "airbag" light coming on at all ?

Answer
Dredo,

First the random misfire code leads me to think the distributor, wires or plugs have a problem.  Oil getting into the cylinders and fouling a plug would indicate bad rings or valve seals.  So, if you are getting that much engine oil into the cylinder a leakdown test has to be performed to make sure the rings are still good.  There is a chance that the blown headgasket broke the rings on the cylinders you indicate.  The second part is the ABS and airbag.  A 2003 should not be doing either at this point.  I would have the airbag system checked due to some problems Nissan was having with airbags loosing communication.  This will tell you which one is defective.  The ABS is probably just the brake system needing to be flushed.  Old brake fluid will compress as it is contaminated and that messes with the brake pressure sensors that communicate with the ABS computer.