I own city 2007 and fortunate for me, I maintain it myself using my own hands and head. Periodic maintenance on EFI vehicle only involves tappet settings, injector cleanup obviously fuel filters changing, throttle body cleaning if not done in last 50k, plugs cleanup, oil and oil filter changeups on time, gear oil changes etc.
I recommend, once you plan to get the tappet adjusted then plan the injector cleans as both jobs require removal of intake manifold on this vehicle and best what you should do is get the fuel filter changed before getting to second half which is removal of intake manifold and further proceeding ahead to injectors and tappet settings.
Injectors clean up after removal and with carburetor cleanup will definitely removes most of the sediments if ultrasonic cleanup machine is not available.
If you are targeting for the mileage improvement then remember that tappet settings, injector cleanup, plugs changing and gap settings is all what is required.
This vehicle easily does 15 to 16 km/L on light foot.