Okie dokie so, firstly yep the rcd510 will work using the normal radio FM on the left of the unit, but no dab.
As for the antenna adapter you don't actually need one, you can just take the plastic off you old single antenna end and then you have the 2 ends to plug into the back of the new unit
Dab wise you can use a windscreen version which cost about £20 (dabonwheels)
http://www.dabonwheels.co.uk/AFAR_Amplified_internal_glass_mount_DAB_car_aerial_.html This is what I used to have and works pretty well bit have since upgraded to a new polo short whip dab roof mounted aerial which replaces the standard aerial with an extension cable run to the front of the car. This is more expensive but signal strength is far superior
Your iPod should work as you mentioned but dot quote me lol