Hi Thinh, I'm a Garden Grove Realtor & resident and know the city well. Without seeing your home and having the opportunity to compare it to recently sold listings, it's tough to give an actual price. I would expect a home in good condition in this neighborhood with 4 bedrooms and 1800 square feet to sell for about $460,000-$475,000. If the home is very impressive it will get more, and if it is in poor condition, it can go as low as $400,000. A cost per square foot analysis doesn't work well for you home because in your neighborhood, there are many homes that are much smaller than yours and have as little as 2 bedrooms.
If you owe more on your home than it's currently worth, there are a few otpions for you to look at. I've posted some information on my website that is helpful for sellers.