To Access The Back Plug You Must Remove The Coil Pack. Remener To Number The Plug Wire, Make It Easier When Pluggin Them Back. I Believe There Are 4 Bolt That You Hafta Remove. Its Easy Like Butter. And Also Use Anti Seize Or Whatever Its Called
Sorry, but DO NOT USE ANY ANTI-SEIZE ON THE PLUGS. That can wind up causing some nasty problems. There's enough oil on the threads most of the time that it shouldn't be a problem. It might take some force to crack them loose, but you don't have to do it again for about 100k miles anyway, so just put them in with nothing on the threads and forget about it.
At 100k miles, you're due for plugs AND wires. On a 94, you need AC-Delco 41-950 plugs and AC-Delco wire set 628Q. You'll pay a few bucks more for them, but the engine was designed and tested with those parts and I think most people here will highly recommend them over anything else. You'll be glad when it's all done.
As for your exhaust sooty smoke, it could be lots of things. Have you checked for codes yet? Is your Service Engine Soon light on? Look at the first thread in this forum "Got codes?" and do what it says. Let us know what the codes are and somebody will be able to help you. My guess is leaking FPR, bad TPS or EGR, dirty injectors, weak fuel pump, or more than one bad O2 sensor. Have any starting problems?