if you want to use the sabot type slugs, then yes get a rifled barrel or rifled choke tube. of the rifled barrels probably the hastings are best, but not cheap. the advantage to the sabot rounds is the trajectory and accuracy beyond 75 yds is a big improvement over traditional slugs. if you are going to put on a rifled barrel then yes, put a scope on it- the cantilever barrels have the scope mount attached to the barrel, so when you swap barrels the scope is still attached and (hopefully) zeroed. sabot slugs can also be 2$ a shell, but the advantages in aiming and low light capabilities are still worthwhile even if you run regular slugs through it.
If you woods hunt where you rarely shoot past 75 or 80 yards-then traditional slugs do fine. they shoot good usually out of a rifled barrel or a smoothbore, individual guns vary greatly. i would encourage you to try the factory barrel. normal foster slugs (win, federal, remington) can be shot through any choke from imp cyl to full, but not extra full or 'turkey' chokes. i have killed deer out to 75 yards the just a bead sighted smoothbore. hope this helps.