Is it necessary to take off the differential cover when you pull the front axle to change the u-joints or will it simply slide in and out. Also is the Rubicon u-joint stronger and will it fit
Pretty much the same as any of the others, I did find it necessary to thoroughly clean the ears as those joints utilize the internal clips on the caps.
Jack up the side of the axle you're working on to keep the diff fluid from coming out once the axle is pulled. Do one side at a time. Be careful putting the axle back in so that you don't damage the inner seal or get debris from the inside of your axle tube into your diff.
Stu's website has great how-to info on our Jeeps, it pays to bookmark it. Here's a great article on how to replace the front axle shaft u-joints. https://www.stu-offroad.com/axle/ujoint1/u-joint-1.htm and how to remove the shafts themselves... https://www.stu-offroad.com/axle/Dana 30/axle-1.htm
The Rubicon u-joints are Spicer 5-760x u-joints. Yes, they'd be a great direct-fit upgrade. They are stronger and more durable than the Spicer 5-297 u-joints the factory installed.