Remove 'bumper' for XM install???
Did the VaisTech SL2Vi for my '08 RX (has nav). You most likely will be looking at the SL2i for Ipod along with the XM kit. Did the install myself, more anxiety than it is difficult, takes about 30min. If your doing XM as well, may be longer to route the antenna wire.
Though there are very nice write-ups on this procedure you can research, if you would like to discuss this on the phone, give me a call. Not one for writing long narratives.
Art: I'll pm you with my tel # if you care to discuss further...