A leaky disposal and tired sink plumbing can turn washing dishes into a daily chore. Once you get it fixed, the kitchen smells better, drains fast, and stops leaking into the cabinet below. You are looking at a couple of hours of work for a plumber, or a solid Saturday if you DIY. Holiday hardware store bundle sales are the best time to catch discounts on units and parts.
Before you buy anything, get at least two quotes from local plumbers so you know what the labor should cost. Never just take the first price you hear. Compare their rates against the cost of doing it yourself with parts from a holiday sale.
Remember that the 0% intro window is a hard deadline, not free money. If you still carry a balance when those 18 months are up, the remaining amount will start accruing interest.