I'm not much positive about Barcelona's chance to eliminate Napoli honestly. Because their game is just not good enough. I believe that they haven't faced a real challenge yet. Porto were the second strongest team in the group but Barcelona won against them twice anyway. But I think Napoli are a bigger challenge than Porto for them.
Napoli have a stronger squad in the first place. They have a very dangerous player like Osimhen in their offense line. They are just trying to improve their form lately. But until this matchup I think Napoli will be in a better shape than now. If Barcelona don't make improvement at the same time then they can really say goodbye to the CL early.
But I think Barcelona was lucky during this season of the Champions League because we know they are not in their best form and this Barcelona we currently see can definitely lose games easily against other teams. While Barcelona is also not in the form to face with stronger teams, however Napoli has players like Osimhen as you just said and since Barcelona's defenders are weak this can be dangerous.
Both teams are currently facing problems with we still have 7 weeks in this first leg match and few changes can create difference with I have feeling despite many challenges Barcelona is much better team from these two in this match and have enough chances to qualify for the next round because Napoli is having problems which can create some mess-up in this transfer window and if they lost their any good player then most chances they could be down in domestic league and their golden period is going to end for another long time.
Barcelona is also in problems, but their coach Xavi is having enough sources to settle things and increase performance level which can bring better results for them in coming days, and they can go through for the top four and also having good chance for the top eight spot in this event.