Sand/stain/seal wood columns

We've got 9 total columns that are all white and would like to be stained to provide a better look on the house. Best practice to go about removing the old paint, staining, and sealing them for longevity? I've considered doing it myself but I currently only have a battery powered Craftsman random orbital sander that probably won't have enough power to knock off all of the paint from the columns. Columns are all wood 6"x6"x8'(guessing on the height, but no taller than that.) Not too concerned about sun damaging the paint as they're fairly covered most of the day and only get the morning sun til about 10am.

While I do think having a belt sander in my arsenal would be cool, I'm not sure I would find much use for it after I do this type of job, especially if I already have the random orbit sander.