Congratualtions on your new FY33!
Might consult your Infiniti dealer performed service history to see where you are on maintenenance. Most here start by replacing or mechanically exchanging all fluids for a baseline. Addding an ATF cooler is mandatory, and thanks to Skibane, it looks best to bypass the OEM "coke can" stock heat exchanger in the bottom of the radiator.
At 100K, you are probably due for plugs, intake manifold, IAC valve, TB, and EGR valve cleaning. Your shocks are probably shot (service history will tell you if they haven't been replaced), but you will neeed to get all the rubber and spring mounts from Joe. Van and Kevin are absolutely reliable to deal with. By following the posts on this board, most of htis can be done by yourself to get your Q45 if top condition.
Yeah, and 20's will definitely stress your suspension and brakes and slow your car down. 18" are probably the best bet unless you drive on airport runways or billiard tables exclusively. How are your brakes? Tension rods?
Be sure to download a FSM and TSB from
http://www.nissan-techinfo.com/infiniti/ for a one day subscription.
And put your good sense filters on when reading posts from some newer members who think Beavis and Butthead are role models when it comes to things like cutting OEM coil springs! Same for removing fender liners if you drive in the real world.
When it comes to parts, OEM is best and Joe is your friend!