Replacing Trunk Filler Panel (also called the upper package tray?)

I have been a lurker here for a long time and have learned a ton. I have searched google and this forum and have not found what I'm looking for. So apologies if I have missed something. My "scuff and shoot" on my 73 z28 has turned into a restoration. Found rot in all the typical spots.
I have rot in the usual place below the rear window. The window channel itself and roof skin is fine. The trunk filler panel and half of the package tray are not. The rot has crept into the quarter panel as well, just slighty though.
My question is, can I replace the package tray and filler panel without removing the quarters? I see there are spot welds holding the quarter panel to the filler panel, which is welded to the drop down brackets (I think I have that right).
Anyway, I have watched Double R's videos but he had the quarters cut out in the area I am asking about. I am hoping to pop a few spot welds loose, cut out the cancer, weld in the replacement panels and then re-weld the few spot welds on the quarter panel that I bust loose. Does that sound like a good plan of attack, or a I missing something here? I dont want to mess with the quarters anymore than just drilling a few spot welds if I dont have to.
Thanks in advance guys. I know many of you have probably been here but I just cant find a definite answer or video.

 

Thank you for the reply and the photos. This gives me hope. Once I start drilling the spot welds and removing metal, we'll see what other surprises may be lurking. In my photos, you can see there is rot in my package tray as well. There has also been a previous repair made to the left quarter panel in the area where it attaches to the filler panel. Looks like this rot was just bondo'd over. This is my first go around with something this big (well, its a big deal in my head) and I'm kind of afraid of it. Just another opportunity to learn I guess.
Thanks again

 

I ordered a full package tray and the filler panel (Camaro Central calls it a Upper Package Tray or Package Tray Extension.....I dont know what to call it lol) from Jegs. The panels are made by AMD and shipping was free!

 

I think I will unfortunately end up going this route. My left quarter looks like someone stick welded a piece of 1/4" steel from underneath and then slapped an inch of body filler over it. I already replaced the upper cowl. Someone had patched the entire upper cowl with fiber glass half way up the driver side A-pillar. Luckily the rot never made it into the actual structure. I had zero plans of going this deep with the car, mainly because I had no idea all of this was hiding.
I'm going to get the DA out and go to bare metal and see what exactly is going on with the left quarter. I know I am going to replace most of the package tray and I think my brackets are ok. Like I said, we'll see as I start cutting out the cancer. Luckily my window channel is relatively fine.

Thanks for all your videos by the way, they have been a great reference.