Did you get the S3W womens' or mens? Not sure if there is a difference other than graphics, maybe someone else will know. The dimensions are different so I think they are different.
I think the length will be fine once you skill up if this was women's ski,
but if this was the men's ski, maybe you could have been OK with the 158 unless you were already advanced skier.
If it feels too long and you can't get it after a day or so, then it's impairing your fun.
It might be worthwhile to go to the rental shop and rent out a pair of shorter intermediate skis (say mid-high 150s length) for a day or two (shouldn't be too expensive), until you can get the technique and swap back into the e3s once you progressed. If you want to go lesson, that's a good idea too if the costs aren't prohibitive.
If the rentalshop has been keeping up to date and refreshed it's learning equipment within the past year or so, the intermediate skis should have a small bit of rocker and big sidecut, and ezmode to quickly to pickup the new tipping-method of skiing too.
If the skis they have don't have rocker maybe go a bit shorter to about low 150s to learn on.
Edited by raytseng - 5/12/12 at 4:33pm