On a scale from 1 to 10 (with 10 being hardest), how hard would it be for a newbie to yank an A2 sight/gas block off and replace it with a railed gas block?

Preparation is usually the key. To be on the safe side, thoroughly soak the two taper pins with Kroil overnight. When the time comes to drive them out, fully support the front sight base. You want the taper pins to absorb all the impact. Brownells sells an AR-15 front sight bench block (part #080-000-252) for $34.97 if you want to spend the money. Wood will work as a support, but if you have a friend's help, your best bet is to put a 4MM socket under the taper pin. It'll support the front sight base, and when you drive the pin out, it'll go down into the socket. Use a 3/32" nail set (found at Lowe's etc.) and a hammer around 16 ounces or so. Give them a couple of good, hard whacks (you don't want to pussyfoot around or you'll just mushroom the pins.) You'll want to drive them out from left to right (the same direction that your takedown pins pull out.) Once they are broke loose, use a 1/8" pin punch to tap them completely out.

Pull the front sight base off the rifle, and take a 1/16" pin punch and drive the gas tube roll pin out. Install the gas tube into the new gas block and pin it in place. Using the gas port in the barrel as a guide, mark top dead center on the barrel's shoulder.  Mark the center of the gas block at its rear, slide it onto the barrel back to the shoulder, and align your two marks. If you are not re-using the handguard cap, at least allow for its thickness and space the gas block that much forward of the barrel's shoulder. Use red Loc-Tite on the gas block's screws and tighten them down.

Thanks guys.   Doesn't sound to technical, just requires a little finesse and know how is all.   Your replies are appreciated.