Hi Nick,
any seal that will fit will do, not like the axle is rotating at any speed, maybe double if if you can get it in the size. As for getting them out you might be able to get them out with a screwdriver, in through the seal part and lever it out. Some come out easily others can be a bit more difficult. Try to minimize the damage to it because they may need to get the right size by measuring it up. $6 sounds about right for a seal that size
