The value of your property is difficult to determine. It's not determined by what you paid for it, or how long you've owned it. It's not determined by you or a Realtor. It's not determined by what similar properties in the area recently sold for....those are "history" and no longer on the market, and most likely, those buyers are no longer looking for property. Generally, actual value is determined by supply and demand.The exact value is determined by what ready, willing and able buyers are willing to pay for it....and that will be determined by what other options are available to those buyers.
The best way to determine the value is to pretend you are a buyer looking for property similar to yours, looking at how those compare to yours, and adjusting the price accordingly. Then, you'll have a starting "list" price. Most property doesn't sell for "list price", so...you'll have to look at recent sales history to see what percentage of the "list" price lots actually sell for.
A good Realtor should be able to help you. Yes, you can try to sell it yourself, and you can do your own open heart surgery, but I wouldn't recommend doing either. Generally, a good Realtor will save you more than they'll cost you, but even if that's not the case, they can make life easier for you and hopefully keep you out of court.
Unfortunately, you are in New York, I'm in Minneapolis, and your property is in California. My suggestion is that you contact a Realtor in California. It's spelled Irwindale...I think....unless you are talking about a place I'm unaware of. Irwindale is in the San Gabriel Valley, in Los Angeles County. I know three good Realtors near Irwindale and would be happy to help you get in touch with them. I'm not licensed in California, but they are and any of them should be able to help you.
Mike Kelcher RES Realty 763-228-2967