Dude, that dealer is pullin' down your pants a little farther with every word they tell you... Don't go in their again, or agree to any work, or you know what will happen...
Screw the headbolt,, ride it out untill it blows.
Oil pressure intermitently dropping is a known defect with oil pressure sensors...
For a near imaginary problem and a $30 sensor, they are going to rake in some big cash from you.
Don't do it buddy.
Get your HeadBolt replaced by a backyard mecahnic. it is not roscket science, and you don't have to pull the head... AutoZone and Napa Sell replacement oil pressure sensors...
Merrick