2000 Pontiac Bonneville 3800 engine tune up

Engine Performance problem
2000 Pontiac Bonneville 6 cyl Front Wheel Drive Automatic 85.000 miles

Hey

I'm, tryin to remove and replace the spark plugs and wires on my 3800. I cant seem to figure out how to acess the 3 rear spark plugs, when I do get my hands on them, I cant seem to be able to pull those metal clips out, that the wire plugs into. Is there a certian way or trick that I dont know about, I got the three front out but by pulling really hard with pliiers, but not the back, any idea?

thanks!