Siding changes

Good morning everyone

I am currently rebuilding my second bathroom (the one in the corridor) and will tear everything appart up to the studs as the previous owner did a terrible job. While I 've been able to preserve the original ceilling - yeah! - (it was covered by sheetrock), I noticed that my sidding is damaged in one section (close to the door). I am looking for any DIY techniques to replace the external siddings (or part of it). I know where to order it but I've never done this part and I am somewhat scared to mess it up. Thanks for your guidance.

Xavier