f40 fuel bladders

HAs anyone had any experience with the replacement of the F40 fuel bladders. I have an Australian delivered car 1990, (similar to a EURO spec car) and according to owners manual etc. etc. the fuel bladders are meant to be replaced after 10 years. I'm not aware of anyone in Australia that has replaced the fuel bladders on their cars. There's about 7 cars in Australia. The local dealer doesn't seem to have an answer either. I have NO leaks, but I would like to try to find out just what goes on with these fuel bladders. I am lead to believe that they sit inside a SEALED fuel tank, so that if they do leak, they only leak into the fuel tank. (not sure if this is correct). Anyone got any info on this. regards....gil