It depends on how deep the details are and how much the existing paint is clogging them. If it isn't too much of an issue, then a simple spraypaint reprime on top is acceptable.
If you are looking to strip a mini, it depends on the material of the figure and the paint type. I regularly use Super Clean to strip eBay second hand tabletop figures. It eats any paint I've thrown at it, without damaging molded plastic figures. However if it is a resin figure, the stuff will melt it.
Good tools once you've soaked a figure in your juice of choice are toothpicks and stiff bristle plastic brushes. Sometimes a resoak is needed. Once I've scrubbed a lot of the surface and picked out the details it is usually good. If original paint exists in a super obscure crevice, it shouldn't matter once new primer goes on.
For something that large and with such largely sculpted details, I'd probably just spray paint over it without stripping.
The paint may end up a little more susceptible to wear than if you strip it, but this is a display piece not a tabletop piece so I imagine it won't get handled nearly as much or as roughly.