The battery tray will get in the way, but a hacksaw will soon fix that
Having to cut the battery tray is about the only con - the pros are having a better quality and more adjustable shock.
Have you fixed the front end first? You should do this because the front is in far more need of being fixed, and you won't appreciate doing the back as much otherwise.
If you've got all the tools/bits you'll need ready (you'll need a new bolt for the bottom of the shock) it can probably be done in an hour or two. If you're new to this kind of thing, I'd aim to do it over a weekend - it's not something you want to rush.
Also, I presume you have a K3/4/5, as I don't think it'll fit a curvey.