Keep the train moving. DO NOT BREAK DOWN.
You and your fellow passengers just wanted a discount ticket, but now you're stuck on a dying train through a seemingly endless prairie. Scavenge the fields for fuel and strip old train factories for parts. Communication is limited outside the train, so plan accordingly.
It's an endless prairie, so burnable fuel shouldn't be a problem. Although some fuel sources are better than others. Remember, just because you can't see in the grass doesn't mean the local wildlife can't.
There are plenty of abandoned train factories along the way too. Since this track is no longer maintained, the train may lose structural integrity. But good news: plenty of parts can be found to repair or upgrade the train. Just remember installing them might take some skill. And be wary: these locations no longer have active security and may have unintended guests.
Just keep in mind that you did this for that wonderful 10% discount! (discount is in the form of a 12-16 week rebate)