Re-building sets - paid services?
With “services”, do you mean someone who would come out to your house and rebuild the sets for you? As intriguing as that sounds, I do not believe something like that exists. Your best bet is to grab an instruction manual and start rebuilding from the pieces. Once you have a few sets built this way, it’ll become easier to rebuild the remaining sets. For sets that you know he has but you cannot find a manual, go to lego.com to download the instructions. Then, once it’s down to a few unknown sets, make pictures of the unusual pieces and post them here - we can help you identify the set(s).