Honestly, it is likely that no one on this board could tell you what effect your car loan being paid off would have on your credit score. Some people could do it, and their score would go up. Some people, it would go down. Others, it wouldn't change. I would advise you to get a good mortgage broker and ask him what it would take to get you into a house. Assume your score won't budge from where it is, because in all likelihood, we have no guaranteed way of raising it. I recall from my house search two years ago: with enough money down, a steady job and no new negative tradelines in the last two years, you can get financed with any score.
i wouldn't pay off the car - it will shorten your average age. with a lower score, you are better off having more money to put down or as "reserves". you need to dispute these items with the CRA's.
