the advice you have been given seems perfectly reasonable to me, although a little more information would have made it clearer. Most gp's will routinely test for cholesterol if you are over a certain age, as they get more "points" for giving lifestyle advice, checking blood pressure routinely eyc etc
High cholesterol foods include things such as cakes, bscuits, saturated fats (animal fats; butter, any fat you cant see through at room temp ie fat on pork chops etc), prawns, eggs cheese, offal. so try to cut those out or reduce the intake of them
Current UK guidelines state that it is desirable to have a total cholesterol level under 5mmol/l, and an LDL level under 3mmol/l.
As the first poster daid, there are 2 types of cholesterol , hdl and ldl. Hdl is "good cholesterol", wheras ldl is "bad cholesterol" you have to have a good ratio of one to the other.
Try this site for more info
http://hcd2.bupa.co.uk/fact_sheets/html/choles terol.html