I assume you wouldn't get the oil seal changed yet if you weren't going on a big trip? Given you aren't heading for a 3rd world country where finding spares or mechanics might be a problem, I would just take some spare oil with me and keep an eye on it. Worst case you'll have to find a garage on the trip. I guess if you wanted to be more careful you could always source a replacement part so if you need if fixed and find a garage you aren't stuck because they'll have to order one and that will take 3 days, etc. But then I come from owning Land Rovers - they always leak and it has to be a really big puddle of oil on the driveway to bother doing anything about it.