Stepping out of the spray won't leave half the bathroom soaked anymore, and cleaning a single sheet of heavy glass takes a fraction of the time of a framed track. The actual install usually takes just a few hours, though you'll wait a couple of weeks while the glass shop cuts and tempers your exact measurements. January is the slow season for most home trades, making it the best time to get contractors on the phone and actually negotiate a fair price.
Never settle on the first quote that lands in your inbox. Get at least three local installers out to look at your walls, because tile out of plumb will need custom cuts that swing the final price by hundreds of dollars.
That 0% window is a hard deadline, not free money, and any balance left when the 18 months run out will trigger high interest charges on what you still owe.