I did five K- Line Train Masters. It took one kit each from NWSL, a " Puller" from the same Co., and about three hours worth of effort, each. I think the most difficult part was coupler pockets.
Two of them had insulated trucks, because I split the steel frame and added an insulator - but the three that I made for me just require a "tender" for pickup. I use express reefers or baggage cars, but anything will do.
If you are not mechanically inclined, consider MTH, where, for the same price, you just drop in wheelsets.