Is this the glass panel you mean?
This is the tool you need to install it:
Unless you already have it you'll have to buy it in order to install the new glass panel, yes.
Show off the inside of your iPhone 4S with a transparent rear panel mod. This back glass replaces your opaque back panel and lets you see the iPhone 4S components inside. Complete with all the necessary parts including camera lens, flash diffuser, and bez — 50+ available at 24.95 each.
Compatible with the type 5IPR fasteners used on the iPhone 4/4S and iPhone 5. Swivel top handle with precision tip driver. — 50+ available at 11.95 each.