which front springs? drop in kits are easy, pull the caps, cut the spacer, drop everything in and recap. standard lowering kits require the fork legs to be removed.
What bags? 4 inch, Screamin Eagle tapered, 6 inch. Slammers are basically the worst possible suspension option in terms of comfort, but that aside, I suspect you will shred pretty much and saddlebags longer than stock length with slammers. Well, if you try to lean into a turn with any vigor.