The KrAZ-255 truck is already available as a model design on this site, and details of the basic truck can be found in the description of that item. This is a crane variant that was developed and used on SAM missile sites to assemble radars, launchers, and to provide general support.
Assembly of the parts should be straightforward, starting with the cab on to the chassis, and working backwards to the crane assembly on the rear. Care needs to be taken to ensure that the spare wheel assembly is mounted accurately so that the crane support is central, but other parts should self-align. The axles are likely to need some filing due to limitations in the FDM printing process, or the holes in the wheels may need opening out somewhat. The mudguards should be positioned as shown in the CAD drawing, and are glued directly to the underside of the cargo body.
The product is offered for personal, non-commercial use under the Attribution-NonCommercial 4.0 International (CC BY-NC 4.0).