what do you mean by how, remove it and replace it

@Ruskes I’m not even sure what “it” is. Obviously I know it’s wood. But is it the door jamb? What can I do to close up that gap? Stick a block of wood there and put some metal capping on it?

based on the photos, the water damage is deeper, probably rotten framing. Open it and take a look. The door threshold still looks fine so far.

It looks like you have siding on the right, but a different surface on the left—is that correct?

We don't know if it's something you can do yourself either. We have no idea of your current knowledge, tools, ability to learn or ability/willingness to buy. Can a DIYer do this? Sure! Can you? Well, honestly, probably, but if you're not sure, you'll face a steep learning curve. I'd encourage you to take the journey, but do a LOT of studying first - you'll have to expose the exterior of your house to the elements while you're fixing this and you don't want weeks of rain while you're learning the next thing. YouTube is good, but be wary, YT is a dumping ground of useless advice, too...

Not just useless, but sometimes flat out wrong and even dangerous. Go find some episodes of This Old House to learn how to do it right. They go over and beyond doing very high end restorations. If you do it 50% as well, you'll be in good shape.

@FreeMan That’s a good point about diy. I have a decent amount of tools and stuff and am willing to buy more. Just not really sure where to start when it comes to my research and that’s why i started here to hopefully be pointed in the right direction. Any suggestions for what I should look into? Thanks! 😊

@Huesmann sorry for the confusion, the second photo in my post is in inside of the house. It’s a laundry room so I wouldn’t be surprised if they just threw some exterior siding on the walls in there

@Kevin is your 2nd pic inside or outside?

@Huesmann just edited my other comment when I realized what you were asking. The second photo is inside the house.

@SteveSh sorry for the confusion, the second photo in my post is inside the house. It’s a laundry room so I wouldn’t be surprised if they used exterior siding on the walls. Wouldn’t be the weirdest thing they’ve done.

@Kevin ah then disregard my original comment. I'm afraid you're gonna need to do some somewhat invasive exploration. You can at least R&R the siding; that might give you an idea of what's happening behind it.

Based on your comments, I've labeled the pics for you. Please make sure the labels are correct. Also, a couple of wider shots showing an overview from inside & outside, for perspective, would help a lot.

@FreeMan thank you! I did put labels in the brackets when I added the pics but I guess they got lost. And I’ll upload some pics of the wider area when I get home. I’m out of town for the next few days

@Huesmann just to make sure I’m following, are you referring to the vinyl siding on the outside or the T-111 (our current guess) on the inside? I guess either would work but I’d think the interior might be a bit easier at first to see what’s going on

The vinyl siding will be much easier to R&R, so start there.

@Kevin those labels only appear when the images don't load or in page readers often used by those with little to no vision. They're good to have, but don't work for the majority of us who can see at least reasonably well.

Having just hung vinyl siding on almost my whole house and preparing to finish, I'm not so sure, @Huesmann, that weaving in a few pieces for a repair is "easier" than fixing up some drywall or simple plywood siding from the inside. Especially when one considers that vinyl siding fades in the sunlight. Our garage, done in "Clay" siding 30 years ago sticks out like a sore thumb from the rest of the house done in "Clay" (from the same manufacturer) over the last several months. A few repair pieces on the garage would be obvious, thus the garage is a strip & replace job now.

@FreeMan I'm not suggesting to replace the siding with new, just to simply R&R the existing siding for inspection access.

R&R must not mean Rest & Relaxation... Repair & Restore? Remove & Replace? Help a brother out here...

I’m guessing he means remove and replace. My only concern with that is this siding is so brittle due to age that I think it would break if I tried to take it off. New siding is on my list of projects, but hoping I can tackle this first.