@Riger
Yeah, gl with that. Since money is an issue NOW. You likely will not be able to age the wine. Also, you expect the current grape production levels can provide enough for an entire territory to thrive off of? Grapes dont grow in a day either, not to mention wine is sometimes tricky to make even with a good quantity of grapes. He even said it himself, he has 1 machine which can make it. So before anything else, you need to overhaul the production, using what was said to be a limited few blacksmiths.
Best part is that he said his own territory was left in a condition which can be described as a wasteland. If that is the case, wtf are you going to export that your own citizens dont need more? Or is he planning to just export anything and everything and buy food for his people?
While it looks good on paper (figuratively speaking), he just invested heavily into a gamble. But this is an Isekai with "modern" technology knowledge, so everything works out 200% better than intended guaranteed.
Honestly, he should look into mead if it does not exist. It is far cheaper and faster to produce. Though it wont sell for as much, your targeted marketing demographic is massive since it is more of a commoners drink. Not to mention the added bonus of bees. They will do wonders at making the wasteland recover. Thus making everything look and feel better to live in. Thus allowing you an option to raise certain land taxes in nicer areas.
Do that and make your high grade wine on the side for special customers of interest like nobles, merchants, and visiting forign dignitaries. Use it as bargening chips for forign aid and developing relationships. It is a good way to show you are not some nobody who just was handed a title since it carries a certain prestige with it.