I am of the opinion that retailer does not seem sincere to you.
Irrespective what the retailer or oil brand says, its best to follow the owners / users manual, especially with regards to drain intervals.
I am quite sure that in your manual, the drain interval would be 5,000 Kms (or 06 months, whichever comes 1st), then why go for 10,000 Kms drain interval?
GOD Forbid, if anything goes bad and wrong with the engine, then that retailer is not going to take any sort of responsibility, nor is he gonna entertain regarding warranty claims.
2ndly, regarding engine oil grade; in this particular case, I won't suggest to go for 0w-20 or 5w-20 oils. The min. should be 5w-30, rest, yours money, yours choice! 