What is the best way to handle implicit performance obligations like installation services, maintenance services, etc. that do not have stated price on the contract and material right related to option to purchase of additional goods and services (ASC 606)? We're using SO as the source transaction and we're sending the invoice to the customer so we don't want the customer to see those implicit performance obligations. We're thinking of including the implicit performance obligations on SO and removing the same on Invoice (and adjusting the price of the retained ones).

I have managed such performance obligations as custom records related to Customer / Project records. This would move the obligation away from simply a "transactional" view to more of a "master data management" situation. These custom records had a life of their own after that. Life of these records was managed by scripts & logic in place such that transactions for things like "renewal" would update these objects. This simplified management of these obligations for purposes beyond just revenue recognition.

What's your estimated (even rough) number of hours to spend to put that script and custom records in place? Were you able to combine promised goods/services (items) into one specific performance obligation?

I would very roughly estimate somewhere between 60-120 hours.