2004 GMC envoy slt xuv , I need a new battery, & want to make sure I get the right size/kind? Also need to find the plug-in cord for the block heater? Please

It's a short in the instrument cluster.
I had the same problem with my 2004 XUV.
It started in early December of 2007.
Intermittent manifestations, than more persistent.
Took it to the GMC Dealer --
Of course, the Truck wouldn't do it's tricks for the Tech.
They replaced the ignition switch and sent me home.
It got progressively worse.
I waited until I was sure it would do it for the tech.
Took it back in to GMC Dealer--
It's a short in the instrument cluster.
They needed to replace the entire cluster.
I bought an extended warranty when I bought the truck.
The warranty is still in effect --
So I only had to pay the $100 deductible.
No Idea what it might cost otherwise.

Neither work? replace the turn signal switch.

The video will show you.
How to GMC Envoy Bose car Stereo radio Removal 2002 2005 replace repair

this is the exploded view of tailgate https://www.gmpartscenter.net/v-2004-gmc-envoy-xuv--sle--4-2l-l6-gas/body--tailgate this is removal and working on an xuv https://www.youtube.com/watch?v=MLQLAD8xOPk

the cord should be routed to the front of the grille area.
The actual heater unit is magneticly attached to the block , and the short cord routed to the front of the vehicle for ease of access.

2004 Envoy xuv 6 cyl when I turn on the A/C the truck stalls but as long as I keep my foot on the gas it will continue to run

More than likely the throttle body needs cleaning

I dont believe its used in your situation .

here is a rundown

Car Radio Battery Constant 12v+ Wire: Orange
Car Radio Accessory Switched 12v+ Wire: The radio harness does not provide a switched power source. Run a wire to the fusebox or ignition switch harness for switched power.
Car Radio Ground Wire: Black/White
Car Radio Illumination Wire: Brown
Car Stereo Dimmer Wire: Gray
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Tan
Left Front Speaker Negative Wire (-): Gray
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Dark Green
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Dark Blue
Right Rear Speaker Negative Wire (-): Light Blue

I also have a 2004 GMC XUV. My gate would go down but not swing open. In trying to fix it, the gate then refused to go to the flat position.I have removed the cover plate on the gate and found the one of the solenoids loose from its mounting. Resetting the computer by disconnecting both battery leads and holding them together for ten seconds worked to restore function to the gate going flat, but the swing still does not work. I believe it is a bad solenoid or motor for the bottem left latch pin.

You most likely have a bad mode actuator. http://forums.trailvoy.com/showthread.php?t=40235