Sampson replaced Stuart Gray after the club made a poor start to the season, but Saturday's 1-0 win over Lincoln extended their unbeaten run to five games in all competitions.
Guinan said: "He has made a huge difference. We are five games unbeaten now and that tells its own story.
"We now have Morecambe and Torquay away which we feel are both winnable games and we have the belief that we can climb this table now.
"If you put a run of five or six wins together then you don't know where you can end up and whatever will happen will happen."