Jacob's is not plug and play. It is easier than the MSD, I heard...I've only done my ICE Pack, so I could be wrong.
You don't get plugs or wires with the kit. the wires can be included, but they cost like $70 more.
You need a new cap if you have a 97 or newer....I have a 94 and used the stock cap.
MSD vs Jacob's is a tough one. People like each....so you'll always get some opinion. as gay as it sounds, the Jacob's being blue was the deciding factor for me....that and it came as a kit that I didn't need to piece together like the MSD.
It took me a few hours to install....finding a switched line that didn't lose power while the car cranked was one of the biggest tasks...then finding room to mount it all was another chore.
I have not seen an increase in my mileage at all. I do beleive it helps throttle response, and you can feel it pull a bit faster i nthe higher revs.