If your native garden was installed properly there is almost no maintenance after the first year. Ok, the truth, it wasn't installed perfectly and those imperfections need some maintenance.
First look and make sure all the things that were installed wrong are corrected. Usually the first thing is to remove the drip. Look at the drip and irrigation pages for more information. Make sure you are watering correctly. Then, put the right mulch down if it wasn't put down.
Sometimes it's easier and cheaper just to replace the whole thing than maintain a disaster. Look for the causes of the problems, not just the problems.
Ok, you did that and all that is really wrong is they got the plant sizing wrong, so look at the pruning page. Or, all that is wrong was no weed control. For more general weed information look at the weeds page. Didn't know you had deer???, look at the deer pages or for other critter problems check out the critter pages.
If something isn't quite right, the plants look funny and you can't figure out why, look at watering or look up each plant, something is probably off. Sun loving plants in shade, shade plants in sun. A plant that grows in the desert next to plants from Eureka means something is going to look bad.
People seem to think because someone is an 'expert' the expert knows all. Most experts just know more than you, read a little and you may know as much. Remember, a native garden should look like a clean and formal park. GENERALLY, the closer the garden is to the native habitat that was there, the less inputs it will require, the less diseases and pests it will have, and the prettier it will be. That's the great thing about native plants, they are native!