Is my head gasket blown really blown?

Okay so the last Wednesday, I was driving and I noticed my temperature gauge go all the way to "H." So I pulled over and it stopped. I drove again and it didn't happen, but I took it to one mechanic and he didn't find anything wrong with my car to cause it to over heat. It was still full of water, coolant, etc. He didn't find why leaks or anything. I JUST got a new radiator, cap, thermostat, etc. Just last November(2014). So it's been over a week and the temperature hasn't gone up again. I'm about to go on a trip from Austin to Dallas and I got it checked by a different mechanic and he said what caused it was a blown head gasket. I don't see how the other mechanic wouldn't see that? I feel like I'm getting played because he's asking for $2500. Not doing that. Do you think my car is safe for this 224 mile drive? I don't want any problems on the road. I don't see any smoke or anything. I'm getting a new car so I just need it to get me there. Thank you! I have a 2004 Honda civic with 241k miles.(it's alot but I'm getting a new car soon!)

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