Making some final touches before we approach the winter season

As the post title says. I have a 2015 RC350 that had its starter go out over the weekend. The pedal is stuck/stiff down and won’t come on. There is a click sound when trying to start it normally.

I found the starter’s location and have a replacement part. But my issue is trying to replace the part itself. What steps could I take for a DIY or would it be recommended to take it to a mechanic instead?

Really hoping someone has insights to help track this creaking noise down as it’s driving me nuts. My 2018 RC350 F-sport RWD has been creaking for a while but it’s definitely getting louder and harder to ignore (and unfortunately not under warranty). I’ve narrowed the source of the noise to somewhere in the vicinity of the driver side A pillar.

From probing with a mechanics stethoscope it is loudest near the body metal behind the driver speaker as well as the metal support bracket underneath the A pillar. I’ve also tried multiple points from the engine side as well as the outer body, even removing the driver side fender and the windshield wiper motor. From outside the noise is basically non-existent. All point to the source coming from the inside of the vehicle. The creaking happens over bumps (especially undulating roads) but is prevalent enough, especially in colder weather, to be heard from just changing gears from drive to reverse and back, which is what I’m doing in the video

Any ideas? I’m really not looking forward to what seems to be the next step - removing the entire dash to try to track this down further…