Advice on/Experience with engine replacement 2.0 TDi

Hi All

For maddening prior reasons and the fact that I have amassed various sunk costs already (mentioned previously in other threads), I am currently exploring an engine (used/reconditioned) replacement for my lovely-but-costly 2015 L&K. Car is generally in good condition apart from the issues that have led to this point, but on a recent garage trip has reported below compression test threshold on one cylinder and at minimum on a second so the time has come to make a decision on next steps.

Does anyone have experience with the engine replacement process generally? And in addition, any specific experience with independent specialists here in Ireland that can be trusted to do the job right? I am considering trying to get a full diagnostic appraisal done before committing to see if I can judge the cost-benefit of the replacement approach so advice on that also welcome. (Not sure if specific recommendations for service providers allowed, but if they are, recommendations for both diagnostics and replacement would be very welcome)