You are about to get a lot more counter space and a spot where people actually gather instead of hovering in the doorway. Installing an island usually takes a few days of messy work once the materials arrive, but planning it for late winter or early spring lets you catch contractors when their schedules are wide open and prices are negotiable. Always get at least three quotes so you know what the local going rate really is.
A project like this runs about $3500 depending on the materials and whether you need plumbing for a sink or electrical for outlets. Spreading that cost out over time makes it manageable, but you need a firm deadline so you do not drag the payments out for years.
That 18-month window is a strict deadline, not free money. If you still have a balance left when the promotional period ends, standard interest rates kick in immediately on what you owe.