It'll most likely help. Opening a new installment loan may lower your scores a bit, but paying down credit cards---especially if lowering them from above 50% to below 50% their credit line (exception: Capital One cards which you'll need to lower below 50% the highest you ever charged on it in any given month)---will raise your scores and likely raise them more than they'd lower by having a new installment loan on file.
Plus, over the long haul, the installment loan will help your FICO.
