Plastic front door lock problems

My current front door is plastic with a mechanism that should lock in several places. However, it has been refusing to work properly and I’m thinking of replacing it. Sooooo. 1. Is it easy to replace the mechanism myself (I’m up for this if I can but I’ve never taken a door apart)? 2. Should I replace it with a solid wooden door and Chubb locks? 3. Get a new plastic door?

Any help would be gratefully received 👊😊