This is one of those times when the answer will depend a lot on the person asking!
We all have different levels of lots of what it takes to dIY things like this. So can I ask a few questions that may lead to better answers, and do it without looking like a jerk for wondering if you can do it?
Some things that need to be asked are just simple things like how you feel about lifting the batteries in and out? That is one that is beginning to get tough for a number of us more "experienced" folks who tend to regret lifting 50-60 pounds!
Then have you done some mechanical work and have some basic tools on hand, so that the main question is more HOW and what to do than WHETHER it is a DIY job?
So maybe give us some ideas of where you are on those things and meanwhile we can begin to talk about what you should find in doing it---if you decide it is something you want to do. Normally changing the batteries is not a big tech issue but more carefully thought out plan for doing the work without creating a ny problems.
And that does bring up one big first question. You mention four batteries but the original drawings for your RV show it might be five?? Looks like two for starting the engine and three for running the RV coach items like lights, fans, furnace,etc.
Maybe things have been changed over the years, so a place to start the discussion might be finding out what you have.
Good idea not to take things apart until we know for sure what each part does as it makes it easier to get it back together!
Looking at this drawing sheet 2 :
https://www.winnebago.com/Files/File...ire_163666.pdf
I did a snip of part of this drawing and did some changes to make it look better for my eye. Seems like they drew the picture with it turned around from what we will see if we look at the batteries, so I turned it over to show more what it looks like if you walk up to the side of the RV. Hope that makes sense for the way you will expect to find it.
Click these snips to get a better view of them.
What they show but this would be if you could stand inside and look at the batteries!
But I turned it around and I think this is what you might see if looking from the outside and things have not been changed over the years?
I think it came with two batteries on the left where I marked in blue and those are to start the chassis engine and run those things like starter. then on the right are three batteries for running the coach things when not plugged in.
Do you have a battery disconnect switch where this shows?
Maybe take a look and see how things may or may not match up as a first step on figuring what you want to do.
RV might be thought of as having three sets of electronics that tie together at times and are seperated at other times. With that in mind, you may want to change out some of the batteries, while other batteries may be good enough for some time yet.
Just trying to get a feel for where you are now before jumping into telling you what needs to be done! And those big decsions are always a personal choice with me!