The gear is basically a hierarchy of parts ...
~CS_LW --> ~CS_LG --> ~CS_LMW --> FUSELAGE
I've explained gear doors
here
what you need to do is combine the two. To get the main wheel to rotate as the whole gear is retracts you need to link it to a dummy "gear door" object (just use a small cube object) If you look in the picture below, the box with the 2 next to it.
You need to call this object ~CS_GD1_ something, this means that it will rotate at the same time as the main gear retracts. You have to add the NUP values as well (see the gear doors link above for more info on NUP stuff)
You can do a similar thing to get the gear to rotate about two axis at the same time (See cube no 1 in pic below) if you have modelled it like the real one it rotates up and forward at the same time !
In a blatant plug for
Expansion Pack 4 if you take a look at the mig 15 thats how I set its gear.