Paint doesn't look bad enough to completely take it down to bare metal. Some spots yeah but not entirely. Just insure the transitions are well feathered. The orig paint that's still good is likely stuck better than what you'll throw on will stick.
DO degrease "before" sanding. I would attack with a 4" sidewinder grinder and a wire brush wheel(wear goggles) then hand sand and feather areas as needed.
"Don't mind me. I'm just here for the alibi"