Oh, and its good to try and get good milage, NEVER NEVER EVER ask the mechanics to do anything related to milage, especially the ones at the toyota's diagnostics section.
For cars like this, changing the oil, air filter and spark plugs is about the maximum you should worry about. Do this:
Change the engine oil / oil filter.
Check the sparkplugs, and replace them if needed
Get a new air filter.
Check other little things such as coolant. a few bolts on earth connections to the body. Terminals on the battery should be in good shape.
Once all this is done, disconnect the negative terminal of the battery for like 10 mins, connect it back firmly, go for a good drive of 10 to 15 kilometers so that the ECU can 'learn' the new parameters. Your car would be as fresh as a new one.