Ok... I'm going to make some guess's on how the wheels are secured based on the video that Keith posted... you'll have to actually look closely yourself to see if I'm guessing correctly or not.
It appears the landing gear itself first has a collar mounted on it, most of these will be retained using a small allen or hex grub screw but it should not need to be removed to get to the wheels if I'm guessing correctly... it's just there to keep the wheels from rubbing against the landing gear wire itself. This is where I'm guessing the most, I think the c clip ( or e clip ) is under the hub cap on the outside of the wheel. If correct, you should be able to pop the hubs off and get at the c clip ( e clip ) from there. I'd suspect getting a set of needlenose into the hub area where I think the clip is will be close to impossible... if so, you'll need to use a small flat bladed screwdriver to remove the clip with. Just remember that the clips like to fly off, so try to block that from happening with your hand or something else that can catch it.