Navisworks Model Simplification for Inventor

I will supply a single .NWD file of an industrial plant. My goal is to have it converted into a lightweight reference model I can drop straight into Autodesk Inventor for clash checks and layout work.

Scope of Work
Open the provided .NWD file in Navisworks Manage or Simulate
Isolate only the required parts of the model (I will provide guidance/screenshots)

Reduce polygon count significantly
Remove small features that don’t affect overall shape
Ensure the model is lightweight and usable in Inventor
Split the model into logical sections if appropriate (e.g. structure, major equipment, etc.) to improve performance and usability
Export Requirements (Strict)

Export the final model as:

OBJ (.obj)

Include associated .MTL file if generated
Maintain correct scale, orientation, and position
Ensure geometry is clean (no duplicates, no broken meshes if possible)
Output Requirements
Model must:
Import into Autodesk Inventor as a mesh without issues
Be lightweight and responsive (this is critical)
Be suitable for visual reference and clearance checking only
Important Notes
This is a reference model only — no need for parametric or editable geometry
Performance is more important than detail
Overly detailed or heavy models will not be accepted
Deliverables
1 × .OBJ file
1 × .MTL file (if applicable)
(Optional) Multiple OBJ files if split into logical sections
Quality Expectation

The final model should be:

Clean
Simplified
Easy to work with inside Inventor without lag

I've attached images of the areas that need isolating, everything else can be removed.