Solidify Complex Hollow CAD Models

I have several STEP files that contain intricate, hollow, or variable-wall-thickness geometry. They feature sweeping curves, blended bends, intersecting holes, and generally irregular surfaces. I need each of these parts converted into a single, fully watertight solid body while preserving every external contour and critical dimension because the finished file will be sent straight to a 3D-printing bureau. You may use any solid-modeling workflow you prefer, but I would like the native deliverable in SolidWorks if possible, along with a neutral STEP of the final solid for verification. Throughout the process the original outside shape must remain untouched; internal voids and stray surfaces have to be resolved so the resulting model imports error-free into common print-prep tools (GrabCAD Print, PreForm, Cura, etc.). Deliverables • SolidWorks part file (.sldprt) containing the complete solid body • STEP file of the same finished solid Acceptance criteria • No open edges, gaps, or self-intersections (passes SolidWorks “Import Diagnostics” and Mesher check) • Deviations from the supplied surface stay within ±0.1 mm overall • File opens in slicing software without repair prompts If this is within your comfort zone, let me know your typical turnaround for a part of this complexity and any questions you need answered up front.