Sure thing! An were all in the same boat here... just learning.
Crutchfield has really great technical support and that's why I chose them for this particular part:
Connect a new car stereo and retain warning chimes in select 2000-05 GM vehicles
www.crutchfield.com
If you look at the harness, it just plugs-into the Buick harness. All "you" need to do is make the correct connections from your radio to the harness.
The above part allows for the retention of the door chimes and so forth. From their website:
Axxess LC-GMRC-04
You want to replace your factory radio, but you'll lose your warning chimes. There's a remedy for this: the Axxess LC-GMRC-04 wiring interface retains your GM vehicle's warning chimes, provides 12-volt accessory power, maintains your balance and fade controls, and keeps the Retained Accessory Power (RAP) feature. The interface also provides the outputs you'll need to connect a NAV receiver, including parking brake and reverse. The interface works with non-amplified systems or when bypassing an amplified system.
Now... as far as the steering wheel controls??? (Yes, this get a bit confusing as now you are adding-in another harness:
Connects your car's steering wheel audio controls to select aftermarket car stereos
www.crutchfield.com
For me... this is where I am a bit confused about things. (One would think it's just joining wires, but...?) Based on my previous experiences with car stereos, I'm going to rely on the Crutchfied Tech support person to walk-me-through this.
I've played around with joining the harnesses "temporarily" and it's getting a bit heavy. (In the past, it was just basically power and speaker wires. Simple.) Now... you might be adding a back-up cam and microphones and other inputs. Choosing a stereo that fits (Depth wise) is also a consideration as BOTH harnesses take-up space.. This is where Crutchfield and purchasing from them is a great asset.
Lastly... I'm not even halfway there on this project. I have the dash apart and just have to figure out how things will be mounted prior to arranging and soldering wires etc. (Lots of ways that can be done also.)
The reason I asked about "another" grounding point was that the wires coming from the Buick side seem pretty thin. Hooking up larger gauge grounds to a single grounding wire seems a bit risky to me. In fact, the ASWC-1 part says: "Connect to a Ground".
As another post mentions.... No problems after so many years... I'm curious how it all fit together.
YouTube videos on the "LeSabre Radio" are few and far between. Nothing really good! Lot's of shots before & after without any real installation content.