Astro AWD Lower Ball Joints

I found my driver's side lower ball joint to be ready to fall apart. I am told that on the AWD you need to replace upper and lower at the same time because you cannot remove the lower if the upper is not removed due to the axle being in the way. When I look at the lower closely, I noticed that it is bolted in place. Can anyone tell me if I do need to replace upper and lower or can I just unbolt and replace the lower. And how big of a job would it be, it looks easy but I have a feeling that this is one of those jobs that is holding a few surprises.

Thanks for any help!

On the upper check them out and if worn out beyond specs rep;ace them to.
And do not forget to check bot sides upper and lower and other front parts at the same time.

Depending on how much you have to replace the job can run from a hr to 4-5 hrs.
Also a front end alignment will need to be done to.