No choice but new engine

I got oil mixing with antifreez real bad in my 97 Altima. I checked my Antifreez resevior and it had a mess of oil in there. I guess my head gasket is shot. I went to 4 different mechanics and all are giving me 7 to $800 price tags on the fix. For that I get a new engine with low miles. I've spent so much money on this car it doesn't make sense donating it and buying a new 1. Does any one have better advice for me? THANKS EVERONE!

700-800 is a good price. if you were closer, i would offer to buy your car if the body is not rusted.