The reason your yellow oil light keeps comming on is due to all this moisture build up in your oil messing with the sensor. The yellow build up around the cap is the highest point that the water vapor can get to and collects there. If the oil on the dip stick looks milky all the way through then you have a headgasket or head problem. If its only around the cap theres nothing to worry about.
Only thing you need to do is change the pcv valve and connecting hoses, change the oil and filter and blow out the moisture buildup inside the level sensor. Just make sure after youve done that wipe off the build up around the cap and see if it comes back.