You have a decent scope (I have the same one on my muzzleloader). In terms of target knobs for it, you have two options. First, you can send it back to Leupold and have them install target knobs (check their web site https://secure.leupold.com/customshop/custom_shop.php
as they have several target knob options). Having Leupold do the work is the best option. Because when they put on the target knobs, your scope will then have "click" adjustments (it does not now). Your second option is to purchase aftermarket target knobs that you can install yourself. It's easily done. You can purchase these type of knobs from Midway USA at: MidwayUSA - Stoney Point Target Knob Leupold Scopes (One Only)
For your technical question as to whether the scope will allow you to make adjustments for a 500+ yard shot, I'll just offer you some tips as I can't answer that specifically. The thing you need to know is how many minutes of angle of adjustment the scope has. If you call Leupold, they could certainly tell you. Then once you know how many minutes of angle of adjustment you have, you will need to look at the cartridge you're shooting and how much your trajectory drops at 500+ yards. If your scope can adjust up, further than your trajectory drops, then it will work. It might not be the best choice, but it will work.
hope that helps.