In my opinion, the job change quest is fairly easy, the only time consuming part is the gathering items part and the marathon/ mushroom gathering part.
You can choose to buy the items and mushrooms, but i'm poor so i did the quest.
In my opinion, mushroom gathering takes longer than the marathon quest because there's like a million people doing the job change at the moment. Too much competition there.
For the marathon quest, Just walk along the edge after the passing the first holes, and there are only two traps that you need to look out for in the entire map.
Count the circles on the floor to know when you need to slow down. Takes around 3 minute to complete 1 round (without any movement speed items, just increase agi)
The whole marathon quest takes around 25 minutes to complete.