How to change spark plugs on 1998 gmc safari?

I want to tune up my van so I took off the housing covering the engine inside my van and I can see the plugs but how do I get to them to change them?How to change spark plugs on 1998 gmc safari?A good assortment of tools. Some you can get to through wheelwell, some from underneath, and some from inside of van after removal of doghouse.