Blown head gasket??

[Spec-R]

(i did search)heres the story, a while back my heater core had a hole and leaked out. i noticed when i was on the highway and my temp went up, i pulled over, and then realized my passeneger floor was covered. got a hew heater core put it in. later i guess i had bubbles in the system becuase i didnt bleed it, my temp went up again, and i got a hairline crack in the radiator,

so i got a new one., driving it around it kept overheating, the temp would go up(i couldnt feel any heat from the heater) then i would drop within a few seconds, now, ive bleed the system a few times, got a nismo thermostat, it hasent overheaded for a week, but when i drive the temp will move back and forth from laying on the C and then a little higher. but when i turn the car off i can hear bubbles in the coolant tank.

and the clincher, is that when i bleed the system and drained the coolant, there were little drops of oil in it. i wasnet alot, just a bunch of little drops here and there.

is this a blown head gasket?? and if so, how much does a new one cost, and how do it do it??