2500 duramax z71

Hey everyone I am new to the forum, so forgive me if this question has already been asked.   I am going to get a 2500 duramax z71 in 5-6 months, and I wanted to make some modifications once purchased.  The problem is since I am new to this kind of thing I don't want some salesman sticking it to me.  

Wants:  I am thinking of adding a 3-4 inch body lift and aftermarket wheels and tires, but I have no idea what size tires I can use with a four inch body lift. 

Use:  I will do mild to moderate off-roading mostly when deer hunting in the fall.

Brand:  By looking at just a couple of 4X4 magazines I can see that there are plenty of accessories to choose from, unfortunately I have no idea what is quality and what is junk.

I will probably have many more questions, but my main concerns are not voiding my warranty, and/or getting screwed in the process.

Don't body lift more than 3". Dont be surprised if there isnt a body lift for a diesel 2500HD, deisel body lifts are rare.

If you are really going to spend $40000 on a brand new truck, why spend $80 to lift it? Do it right and get a suspension lift.

With most dealerships, as soon as you put on a tire 1" bigger than stock, lots of the warranty is voided (including engine warranty as speed sensors cannot function properly). I cant think of many dealers that will allow a body lift while under warranty, and none will allow a suspension lift.

A truck with a warranty isnt meant to be modified. Buy one 2-3 years old, it'll be a 1/3 cheaper and you'll have more money to build your rig right.

Goodluck.

Look for dealerships that carry dealer installed items not voiding out the warranty. Check the factory installed items but usually they install high quality stuff because its all warrantied.