I would have a plan and schedule worked out before bringing him home. If you could exercise and do some training before work and then right after work, with some quality time before bed, he should be fine. The dog walker could be a good idea if the dog is of the right temperament.
Changing his routine is fine as long as things are as clear and predictable as possible when the change happens. Some would advocate the 2 week shut down. I have no experience with this but it has many supporters.
I find that quantity is not as important as quality when considering the time spent with the dog.
When a dog saves the life of a man, it becomes clear that partnership knows no bounds.
Fama - T.E.D.D. OEF XI-XII (GSD)(RET)
Marshall - T.E.D.D. OEF XII-XIII (Lab)(SF EDD)
Lucian - Med Alert / Mobility SD (Cane Corso)
Pud - the old man (Pit x Lab)