Software/technical due diligence in a small business acquisition

I’m currently evaluating a small industrial equipment manufacturer. It’s not a SaaS business but does have proprietary software embedded in its equipment, and the CIM claims the software is a meaningful competitive advantage vs other equipment in the market. Since I’m not a programmer, I’m considering hiring a third party to do a focused software diligence review to better understand what I am acquiring, what know how needs to transfer post-close and whether a go-forward team could maintain it. For anyone who has done this in a small business transaction: 1. Why did you decide to use a third party? 2. What scope did you ask them to cover? 3. What did it cost? 4. Was it worth it? 5. Are there any firms or individuals you’d recommend for this type of review, especially for embedded software/industrial controls (rather than SaaS)? 6. Any lessons learned? Thanks!