The BRP oil change kits are $90. Includes oil, filter, oring, and new crush washers. Have a 14 Ace 900, and the motor/chassis was designed very well to accomadate oil changes and is extremely easy.
My plan is to change the oil, filter, whole sha-bang every other year, but drain and refill just strictly the oil every year.
As far as the cost comparison to a 2 stroke, yes, majority of 2 stroke injector oil is $50/gal and most sledders burn probably 2 gallons a season, Therefore making the cost of owning a 4s not any cheaper. Most 4s are more efficient on fuel though, and the motor will outlast a 2s tenfold.
If you’re not rebuilding your own 2 strokes, most dealers charge $2k+ just for a top end, which is where you’re going to save in the long run owning a 4s. At one point a few years ago I owned 5 sleds, and I had done a top end rebuild on 4/5 of them. It gets old after awhile! 4s isn’t for anyone but just trying to give some perspective!