Mount Koya Overnight

I want to spend the night in one of the Mount Koya Temples, would arriving at 3pm give me enough time to walk around the area before/after dinner? (I'm a quick walker)

Depends what you want to see. The immediate area around your lodging temple, sure. The cemetery? Probably not. Oku-no-in is huge, and you may have to take the bus to get there depending on where your lodging temple is.

You'll have time to walk around in the morning also.

I would think 3pm is plenty of time. The cemetery is big but not that big.
If you stay central:
Takes about half an hour to walk. An hour to get there and back, faster if you take the bus.

Also taking a walk in the middle of the night or early morning is part of the experience.

Thanks everyone, I think it'll work out

would love to know where you stayed? or staying that is most central? the only onsen is booked during our time there -- any one recommend another good lodging that has clean/decent baths?
thank you!

I intend to visit Mount Koya from Nara. Leaving between 8:00-9:00 in the morning and stay overnight at the temple. What is your proposal regarding the itinerary. Do I have to book the temple stay in advance? How to go about it?