What you're referring to is called a Split Prism focusing screen, and if you take the lens off your camera body you can see yours: look up into the viewfinder from the mount. On dSLRs its matte (just flat) and has nothing on it: the 3 marks are electronically added.
You dont use the focus marks in the viewfinder for focusing: you judge and, if you'd like, use the small MF dot in the bottom right of your viewfinder (its a little circular light and lights up when youre in focus).
Also keep in mind that your focusing will be at f/1.8, which is very thin especially with close subjects, so it can be finicky.
Imno expert, but it's usually possible to replace focusing screens: I do believe that on the D60 is voids the warranty.
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