porsche 944

I am interested in buying a 1983 porsche 944 non turbo. can you turbo this car with out replacing the whole engine? also maybe someone can help with with why these car are being sold for so much? in the blue book it says a car in excellent condition is worth 2,850 us dollars. but i can only find cars in bad shape for that much. thanks for the help.

I am in the same situation, there is a 944 non turbo that im looking at but i first want to know if you can bolt on a turbo..