This from the owners manual ( available for download from here). Since there is a filter on the inside of the transmission, it would most certainly require a removal of the pan.
Change automatic transmission fluid and filter (severe service).
50,000 100,000 150,000 mile
Change automatic transmission fluid and filter (normal service).
You can get great information about your H3 from here.
Amazingly enough, not every H3 has a drain plug in the transmission oil pan. That would mean they would definitely having to pull the pan. The manual say this about the How-to:" "Raise and support the vehicle.
1. Insert a flat-bladed tool between the range selector cable end (5) and the range
selector lever (1).
2. Pry the range selector cable end (5) away from the range selector lever (1).
3. Remove the bolts securing the transmission range selector cable bracket to the transmission.
4. Position the transmission range selector cable bracket aside for clearance while lowering the pan.
5. Position an appropriate container under the transmission oil pan.
6. Remove the oil pan bolts from the front and sides of the pan only.
7. Loosen the rear oil pan bolts approximately 4 turns.
8. Lightly tap the oil pan with a rubber mallet in order to loosen the pan, allow the transmission fluid to drain into the container.
9. Remove the remaining oil pan bolts.
10. Remove the oil pan and the gasket.
11. Grasp firmly while pulling down with a twisting motion in order to remove the filter.
12. Remove the filter seal. The filter seal may be stuck in the pump; if necessary, carefully use pliers or another suitable tool to remove the seal. Discard the seal.
13. Inspect the fluid color.
14. Inspect the filter. The filter may contain the following evidence for root cause diagnosis:
Bronze slivers indicating bushing wear
15. Clean the transmission case and the oil pan gasket surfaces with solvent and air dry. All traces of the old gasket material must be removed." So, looks like pulling the pan and replacing the gasket is the way the manual recommends. Hope this helps, good luck.