Yeah I wouldn't kill yourself trying to get the end cap out. I'm trying to remember off the top of my head exactly how I did mine, don't remember having too much trouble with the cap. I didn't have to use heat, but I do recall having to file down some minor tool marks I left while removing the cap. What I cannot remember is what tool I made the marks with lol.
Like I said, I've never heard of one of these failing from lack of lubrication. It's more common that the drive end of hte pinion shaft breaks off. If your endcap won't come off, I would just squeeze it as full of grease as possible. Don't over-do it too much but I imagine any excess would simply squeeze out of the seal or other gaps, that area is not exactly water-tight although it's protected fairly well.
The points that will not get properly lubed are:
1. The pinion shaft end runs in a depression that's on the inside of the endcap. No bearing, no bushing, just a hole in the aluminum cap that the end of the steel shaft runs in.
2. On the other end of the shaft, the cable end, the shaft passes through a hole in the pinion gear housing. Again no bearing or bushing or anything. I don't even think there are any thrust washers in there.
But, if you get enough grease into the pinion gear housing then the fling effect once things start moving should get at least SOME lubrication to these two points. Should be fine.
mystic_1