If it was overfueling yes it would flood. But cant see it overfueling from just changing the plugs. if worried disconnect cold star valve but dont think theres much need. it sounds like yu've knocked summit off when changing the plugs, did you touch the distributor at all, or anything else other than the plug ends of the HT leads? if one plug wasnt done up proper it may not start or struggle as no compression. . did you try it with the old plugs back in, are the gapped correctly and were they all tightened up proper? may sound daft but i'd check all of that! firstly i'd stick the old plugs back in and take it from there.