my truck is 2006 GMC Z-71 extended cab with 5.3 engine....got 237,000 miles on it...runs great,burns 1/2 quart of oil between changes (5000 miles),no rust and still looks good...probably cost $40,000 to replace the truck with a new one and considering dropping a new engine in this truck at some point.....
tried to do some research on a crate engine without much success....can I buy a new either Cheverolet or GMC engine? does it have to bought from a Chevrolet/GMC dealer? what kind of cost am I looking at for the engine and installation cost?
appreciate any advice....

You can buy either as long as the sensors and ECU match. The motors are the same, but I remember GMC having more of those fancy plastic covers, etc.

Installation would be around $750-1300 in labor. You need to consider the consumable parts like, belts, hoses, oil, radiator fluid, etc... That's always extra.

I want to go to your mechanic! $750 to remove and replace an engine in a 2006 truck is a steal.

The cost can’t be estimated without more data. Short block? Long block? Dressed long block?

If you want to compare some things go to Summit Racing and research their crate motors.

I entered the year/model info on my truck and the decription info on the replacement engine is that it is a remanufactored engine....does that it mean it is a used engine that they have replaced worn parts?....I would prefer a new engine...is it possible or affordable to buy a new engine?...

Might consider having your engine rebuilt since the block and heads are in good condition.

Yes, Scroll down to the crate engine section and open that up and look at all the different options

You'll probably need a transmission rebuild as well, plus ECU, etcetc. Expect for your truck to be down for quite a while and the cost to be double what you expected.

must be doing something wrong-all i"m getting is high horsepower models......

want to do it right and get some great mileage go to an ls3 (350 small block).

for a straight replacement, jegs, summit or my preference is a dealer/new factory crate engine.
if you buy from a dealer get a package price for purchase/install out the door, you will also have a useable warranty should you need something fixed.

https://www.gmperformancemotor.com/category/SB.html

I have installed my own multiple times, short blocks to dressed long blocks, pay a dealer to do it.

DO NOT even consider auto zone, oriellys, pep boys etc. for one.

thanks for the advice/help.....