I want to get a aftermarket radio for my 2002 nissan maxima. Couple things.

1. i want to put in the head unit before putting in the adapter, would i have to install the adpater when i put the head unit in or can i wait?

2. i herd when some people had install the adpater they lose the trip button, how can i prevent that from happening?

 

You can put in the head unit first, just make sure you have a head unit with a wired remote connection, some don't making this option useless. After you have it installed, whenever you'd like you can easily install one afterwards.

http://www.amazon.com/Metra-ASWC-Uni.../dp/B0039H2W66

This is the one I use, works flawless, automatically programmed and super easy to install.
In order to keep the trip button working, you need to ground the brown wire on one of the three harnesses that plug into the OEM radio. Also in the instructions for the Metra unit, I think they tell you that you need to ground that wire for it to work.

 

^^^this

 

+1. ASWC works flawlessly.