A worn leather interior makes even a well-maintained car feel tired every time you slide behind the wheel. Replacing the upholstery gives you that new-car smell and feel back, but it is a serious chunk of change to drop all at once. The best time to book this job is right after tax season, when upholstery shops often see a lull before the summer rush and might be more willing to deal on labor.
Before we talk about how to spread out the payments, separate the negotiation from the financing. Walk into the shop and negotiate the cash price for the materials and labor first, treating it like any other big-ticket service. Only bring up payment tools after you have agreed on the final bottom line for the seats.
Keep in mind that the 0% intro window is a hard deadline, not free money. If you still have a balance left on the Citi Simplicity® Credit Card when those 18 months are up, the remaining amount will start getting hit with regular interest, wiping out the benefit of the plan.