RE: KV Rating??
Typical hobbyshop if they don't know you [:@]. Yeah, you'll need a gearbox depending on the plane of at leats 2:1 reduction. What plane is it going in? I use a himaxx 2025 4200 on 3s lipo for several applications from fast pusher jets to slowflyers to 3d planes. Geared 2:1 with a 5x5 prop in a small pusher it screams, but geared 10:1 and with a 10x6 prop I can slow fly for a loooong time. If it is a himax motor there are several gearboxes that work well. For large reductions I use gws gearboxes. Hope this helps! If you don't want to deal with gears, take it back and trade it in for something like a 1500-2100kv rated motor.