Problems with creating a skeletal mesh for a car model in blender

Hello, I did a post a while back and I’m still stuck with my car model(I found the model on a free website) in blender, and I really need some help. I’m trying to develop a small vehicular combat game to finish college, and found some obstacles since I’m new at unreal(really new) and have little experience(almost none) with modeling. Any help will do.

So, to edit the model in blender I followed some steps, watched some videos and found a really helpful post about it(Export Rigged Model From Blender To UE4 - Animation - Unreal Engine Forums). Although the post was about a mech model, **DyotoOrion **said the way OSUNightfall(the guy who created the post) was rigging in the wrong way, and the right way is to have all mesh objects contained inside one single mesh, and then the single mesh should be parented and vertex weighted to the skeleton. He also said the only reason to rig with separate objects is for vehicle suspension(witch I want to have with my car).

Here’s the situation. At first the model was a single mesh, and I made some alterations:

  1. Separated and joined the correct parts to have body + wheels of the car;
  2. created an armature and then add a bone for each wheel(5 bones in total);
  3. Corrected the center of each wheel.

I didn’t do any parenting and vertex group yet. This is what I have now:

I have a lot of questions, but all I want to know right now is: what I’m doing wrong? I know that I have to associate each wheel for it’s respective bone but the way I was doing before was wrong.
In the end, I’ll have to join the mesh objects(body+wheels) into a single mesh or no(since I want to add vehicle suspension)? I don’t know if that’s even possible in this case.
When creating the vertex groups, how should I set things right with the bones?
Finally, please, any advice would be appreciated. I’m kinda lost here. Also, the link to my model and other pics :