A new sliding patio door changes the whole feel of your living space. You get better light, a tighter seal against the elements, and an easier way to get to the backyard. Getting this done early in the spring is smart because you beat the rush when everyone else suddenly decides to renovate.
Labor rates for contractors tend to climb as the weather warms up and their schedules fill. Aim to get your quotes while it is still cool out. You will want to give yourself a few weeks to find a crew before the busy season hits.
Remember that the 0% intro APR is a deadline, not free money. If you have a remaining balance on the card after the 15 months are up, you will start paying interest on whatever is left, which will quickly make the door more expensive.