Ryan, unfortunately, things like the blinds go to the cheapest bidder, as with most other things in our ovepriced RV's!
Things just are not made to last anymore.....:(
But putting that aside and answering your question, yes this can be a DIY thing to fix. I am a fix it guy and refuse to throw anything out if I think I can repair it.
I have taken apart many blinds and fixed them.
First find a replacement cord and buy a bunch. It is dirt cheap to buy so why not get 50 feet to have some on hand for future repairs. The trick is to find a better quality strong cord.
Remove the blind from its mounts and you will find the cords go into the top and get tied to the controls. Note the routing and undo them one at a time and pull it out, following the path with the new cord. You can even tie the old to the new to pull it in to follow the same path. Just be careful with the slats so you don't bend them.
Bottom of the blind usually has little buttons to pry off to expose the knot at the bottom to hold it in place.
When you "tie the knot" (lol), use a double loop and pull the knot tight. That is, instead of looping it through itself once, go around twice or 3 times through itself before pulling the knot tight. This gives you a bigger knot that is less likely to pull through the hole, and also is less likely to come undone.
Once you have it re-threaded, you will likely have to undo the knot at the pull cord end and "equalize" the 2 or 3 cords so they all pull equally on the blind.
As a hint to help against future wear on the cords, especially if they go up and down a lot, assist the blind going up by raising the bottom of the blind up with your hand as you draw on the cord to open it. This will reduce the stress on the cord where it goes through the lock mechanism of the cords.
You can do it - you da man!!