Please help- have I been ripped off?

I have a 92 Honda Civic with about 280,000 miles. The check engine light came on and I noticed that the radiator had no water/coolant. After filling it, I took it into the shop. The mechanic told me that after reading the code, they suspected that the radiator had a leak but it was minimal and didn't need to be fixed. The major problem identified was a bad radiator cap that needed to be replaced. The mechanic hit me with a bill for $169- labor was 1 1/2 hours @ $90/hr and the radiator cap was like $20. When I picked up the car, I noticed it was shaking incessantly. I called the shop the following day and they asked me to bring it back in and they suspected and confirmed that my head gasket has blown. The mechanic told me that I need to start looking for a new car because it would cost me more to fix the head gasket than my car is worth. He adviced me to start looking for a car as it was inevitable that my car would die and in the meanwhile to keep adding water and drive locally. I feel like I wasted money paying for them to fix it and I'm wondering if I have been ripped off- leading to my next 3 questions.

1. How can I get my car to last for as long as it's possible with a blown head gasket? I assume I should always put water in the radiator before I make a trip- is that all I can do or is there something else I can also do that will slow down the death of the car?

2. Considering that I informed them that my radiator had been completely empty at the time that the check engine light came on, is 1 1/2hrs a reasonable amount of time to interpret the code (stored in the car's computer) and to put on a radiator cap? Have I been ripped off because I'm a woman and clueless about cars.

3. Shouldn't the diagnostic test they ran to figure out the code have revealed that it was a blown head gasket instead of charging me such a huge lump? I feel like I paid for nothing. Do I have justification for reporting to BBB?