Never hurts to have more picks, but in just about all cases, will be some sort of plastic or rubber strip that sits in a channel to hold the glass. If I said it is always on the outside, I bet I would be wrong. I just never seen them on the inside, unless the window was installed backwards, I have seen that.
But yeah, will need a tall ladder to reach that window and will be outside working on it.
You want to be careful removing the strips, a small thin pry tool and be gentle, you may or may not be able to find a replacement if you damage beyond repair removing them, will be another issue that can be fixed.
One more thing, if it is dual pane glass, you will need to measure it and call your local glass store and order it.
They will call their supplier and order it to the size you give them, because of the process to make them. Just be sure to order the glass first, or expect to cover it up while you wait for new to be delivered.
And is best to have a helper for this job, The suction cups that Joe pointed to is a great idea, one person outside with the cups pulling, while helper is inside and using a thin blade to cut loose the adhesive or whatever is used to hold your glass in.