[vin63]

If there is only a slight build up, as you mentioned, you can probably get away with cleaning the valve cover(s) and then just running a premium synthetic oil for 3K miles (making sure you do several long drives), changing the oil filter at 1K or 1.5K mile intervals. As a long-time lubricants retailer, this is what I recommend before doing an complete engine flush.

A premium synthetic oil, such as Mobil 1 and Amsoil (both processed from group IV base stocks), will do a better-than-expeted job of cleaning the inside of your engine. One drawback to look out for, is that because of the cleaning and ultra-slick properties of these oils, you may find oil leaks that you didn't have prior. Typically, this usually around the oil pan gasket and front/rear seals, but if you are going to change those out anyway, then you are most likely fine. Good luck.