Going to be picking up a new deck for my 99 GTP this weekend and outside of the radio likely not mounting flush, is there anything else I should be mindful about?

Steering wheel controls won't work I suppose but not a huge loss, and its just the basic factory radio. Is there any nonsense to deal with the security system?

The speakers have already been swapped out before I bought the car so a new deck should perk them up nicely.

Any insight is appreciated thanks!