1992 Mitsubishi Diamante engine repair info

1992 Mitsubishi Diamante mileage: 110,000. I was told my car needed the valve seals in the engine replaced, and my husband wants to do the work himself. The problem is we can't find a repair manual or any other information to help him. Can you help us find any kind of manual, video, etc. For my car? Can you give me any advice on any of the above to replace the valve seals and/or rebuild the whole engine? Any help you can provide will be greatly appreciated, if my husband can do the work himself it will save us at least $1,500.00.