I found the answer (see below) posted on another web site. I followed the instructions and replaced the spring. I found, as the original poster had, that the new spring works better than the original and is much more sturdy. To the original instructions, I would add the following:
1) There are about 20 screws so have patience removing and replacing the screws.
2) Step 3, "Slide off the rear panel" requires further clarification as the panel will not slide off even with all screws removed. I had to turn the oven over, with the top of the oven sitting on the work table. I then used a screw driver to lift the two tabs that hold the back panel to the bottom panel. With the tabs lifted, the back panel will rotate away from the oven along the edge where back panel slides into the top panel. The back panel can then be slid out. I have included three photos that show this step.
3) Step 7, "Re-attach feet": Be sure to use the guides on the bottom of the oven to slide the foot assembly onto the oven. I had unsuccessfully tried to screw the feet onto the oven without using the guides.
Oringinal instructions for replacing the broken spring:
Just repaired this yesterday.
Got a spring from Lowes (Hillman Part # 543028 for about $4), it's larger than the original but seems much sturdier, original is really thin metal. Fit the space provided without problem.
Oddly, end result was a more 'giving' spring action, prefer it to original, which loved to snap shut unless door was 100% opened (ie fully 90 degree open).
This is for BOV800XL:
1. Remove all rear screws
2. Remove feet entirely
3. Slide off rear panel
4. I was not able to remove top housing - but I was able to gently pry sides open just enough to thread the new spring with a little ingenuity and effort. Watch out for sharp metal edges everywhere.
5. Slide back in (remember that top edge goes under the top edge/lip)
6. Put all screws back in
7. Re-attach feet