About to change spark plugs on my 04 GTP with colder ones in preparation for modding season. I have no idea how long this will take, given that I can't see 3 of the plugs when I install them (the ones in the back, of course). Suggestions? Tips? Tricks? Or should I get a place like Pepboys to do it for me? If I can definitely do it myself I'm all for it. I'm just wondering if it's too much of a PITA.