This is a serious thing to r do correctly the first time, because your engine can be ruined if it is not lined up perfectly. I would go to www.alldatadiy.com and pay the fee for the factory service instructions.
I had to replace my timing chain on my 2000 Altima and It's not fun at all. Setting the timing chain is not hard to figure out. Many part store web sites have free tech manuals online. Make sure you replace the two chain tensioners! These are what fail after 150000 miles. To set the timing chain correctly, you will see that the chain has a marked (colored) link on the chain, this must line up with one of the dots on the cam gear-you will see this explained in detail with photo in any good manual.Remember to replace both left and right tensioner of the main single chain, mine failed at 181000 miles.