Radiator replacement can be pretty simple. You can possibly remove the rad and take it to a rad shop and have them repair it for fairly cheap, however you can probably also find a relatively cheap new aftermarket rad. If I was you I’d flush that rad leak stop out as soon as possible because that shit is snake oil and will only cause you headaches in the long run.

It’s definitely a gamble with a Facebook mechanic. If he doesn’t have a shop/business then don’t expect any sort of warranty on his work.

Do you have any abs lights on or steering fault messages present? It’s possible you damaged a speed sensor or tone ring when doing the wheel bearing. A bad speed sensor can cause issues with your power steering as it needs to know the vehicle speed to determine how much steering assist you need.