That game is... the big one. I finally got around to learning V2 lately, but still very much afraid of HoI. Hopefully I'll get to that at one point.
If you can manage V2, the HoI franchise shouldn't be a big problem. HoI 3 is probably the most accessible game they made aside from CK2 (and maybe Sengoku, I haven't played that because everyone said it was shit)