1987 gmc. 6.2 litre diesel. 4wheel drive. Auto Not my truck. Helping a friend get his truck running. Just put in a new engine and truck will not stay running. Have too crank for a minute to start and then will die after 30 seconds. He was told it was the injection pump. Leaks around seals.

My questions are;
Are special tools required to change the pump?
What is the easiest way too do it?
How do you line it up(timing)?

Any help or suggestions would be greatly appreciated. I am not very knowledgeable with diesels, but have gotten very good advice from this forum before. thanks
jim