Installing Android apps is as easy as installing native apps. A popular app store for Android apps is Aurora store.
So far, Jolla was very good with spare part supply. You could get for instance new screens or batteries for the Jolla 1 (from 2013) even in 2023. They already have repair kits for instance for the camera glass covers of the new Jolla Phone 2026. This is written in their blog in this forum: