You’re overthinking this. You can almost always get by with whatever system you already have available, until you get a full job, at which point the job will probably provide you with a machine.
I think you’re misunderstanding the insert method. insert keeps everything that was already in the list, including the item at the given index. it just shifts part of it to the right to make room for the thing you’re inserting. Directly changing the list using display[position] = letter instead replaces the item at the index with letter.
You’re overthinking this. You can almost always get by with whatever system you already have available, until you get a full job, at which point the job will probably provide you with a machine.