u/CosmoGnat

I've got to do some repair on my new home (built in 1910), and most of the windows need this wooden casing (?) around the vinyl window scraped and painted, but a few of them need to have some of the wood replaced. I don't know enough to know what this exterior wooden bit is called so that I can start to figure out IF I can do it myself, or if I need to hire someone.

Any insight? I've googled diagrams but nothing looks quite right in terms of what is labelled, would appreciate the help.