I agree, go for the 4-Star. Don't get me wrong, the SS-60 is an EXCELLENT airplane and I love mine. It's a little on the heavy side though, pretty fast and actually very maneuverable. This makes it more of a 3'rd plane in my opinion. The SS-60 kit is also a much older design and doesn't build quite as easy as the 4*. Still, I highly recommend the SS-60 at some point down the road.

I'd run the 4-star gear as is. The wing structure doesn't really lend itself well to putting the gear there.

Engine choice is easy... OS .61-FX or OS .75-AX. Both will usually work well right out of the box.