I think you just push the top part of the clip over to the side it it slides out of the bottom half. Or, you just stick a screwdriver in the clip at the end and pry it apart (its been a while since I've messed with them and these are the styles I can remember coming across). The plastic is rubbery so it should bend long before it breaks. As far as new plug wires, yeah I'd say it would make a difference. How much? I don't know. If its running good the way it is just leave it alone if you want. But, with 175,000 miles on it, it may be best to go ahead and change the wires too. Definitely couldn't be a bad thing if you did.

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2004 XLT 4.0 4x4, 3" PA body lift, 32" BFG M/Ts, Dick Cepek DC-2 wheels, Euro tailights, self-painted headlight mod, NAV/DVD/XM/iPod stereo (Pioneer AVIC-D3), Line-X, Westin step bars, AVS bug shield and window vents