Service book stamps make no difference, except to idiots that read used car guides, and think their car will get what it says its worth on parkers.
Depends, Something real luxury or high performance will hold more value if its been done at the dealers. Would you buy a Bentley or 911 if it had been done at "Backstreet Motors" for its entire life, or would you want to see its been looked after by the dealer from new?