Right, firstly I need to know if your car is an X3 or LC (model number that just defines the shape - you'll see it a lot around the forum). Normally, a T-reg is 1999, with V-reg for 2000. However, there were a few T-reg and V-reg LC's as they were supposedly released in late 1999.
If it's an X3, it'll look like the yellow one in my signature, if it's an LC, it'll be more "angular".
If you have an X3, the fuel filter should be somewhere on the engine bay firewall (between the engine and cabin) - you'll have to trace the fuel lines back from the fuel rail to find it as no-one's ever managed to get a decent picture of it.
If it's an LC, the fuel filter is attached to the fuel pump in the tank. You'll have to remove the rear seat cushion and then the cover on the metal bodywork underneath ... then it's just a case of unbolting the fuel pump cover to get access to the tank (and the filter). It's fiddly, but do-able. Also, make sure you have pleanty of rags or other absorbant cloth to absorb any spillage - you don't wan't the car reaking of fuel.
Finally, before disconnecting the fuel lines, locate the fuel pump fuse and remove it. Then start the car. It will cut out after a few seconds, which is normal. This will remove the majority of pressure in the fuel lines and make it safer to disconnect any fuel lines necessary