Hmm.. I'd say you need to pull the code and see what it says.. Maybe a harbor freight store would have a cheap one? Have to wonder how trashed the old plugs were? "Almost" sounds like its having AFR issues.. I'd be about tempted to let it idle for a few minutes then lightly blip the throttle.. as long as the check engine light didn't come up.

EDIT:
Just checked harbor freight.. no cheap ones.. got mine on Amazon for about 18 bucks but I don't think your wanting to wait on shipping on this deal..
And since your not running off anywhere in it soon... (sorry..lol)... I'd be real tempted to pull the easiest plug and recheck that "pre gapped for your convience" feature.. Had them before I had to fix...