How can I easiest (cheapest) I'm within EMC regulations?
If your product needs formal compliance testing, you unfortunately need to have an accredited lab do the testing. [Edit] It's surprising to me that this product cannot be self-certified, but it sounds like you've determined it is necessary

At my workplace, we'll do pre-compliance verification using either a GTEM cell or a spectrum analyzer and near-field probe, essentially to validate that the product is ready for formal testing. In your scenario, I'd say near-field probe and spectrum analyzer is the way to go.

As expensive as compliance testing is, anything you can do to make sure you only have to do it once is important.