Listen to this ^ 100% agree.With $6k, I'd spend that all on a refresh and baseline on the rig. Just to make sure it drives close to new and it's as dependable as I can get it. That emptied about $6k for me.
I was once exactly in your shoes thinking I had $ for mods with my 2002 that had 170k miles at the time. Well, get your rig up to 100% spec before spending it on mods. That's the best thing you can do. Mods are pretty worthless when your 100 is old and worn out needing a bunch of stuff.
Even if you claim your 100 was maintained to the T, there's always something.
The best off-road experience isn't a modded up 100. They are nice to have but the best off-road experience is on a baselined, up to spec, 4x4 because it takes a lot of question out of the equation. Like previous comments have said before the stock 100 is a pretty damn good and capable 4x4.