you might be able to leave all of that attached, to remove the ignition lock you need to drill a small hole in the steering lock housing. If you can get the drill in the right spot you wont need to touch the spline adaptor. In fact, you might find the hole is already there as it looks to be an original lock housing with an aftermarket lock.
Take off the upper plastic trim and have a look! If there is no hole, you need a 3mm drill bit and drill as follows:
