First of all, this is all state-dependent. So you have to know the procedure for your state.
Second of all, as you know, when you create your LLC (Main Street Estates, LLC) this is usually done with some forms that you can find online and the place to start is the SoS. You submit the forms and some money and you get back a filing number and go into a public database.
Third of all, you will probably want to open a bank account. You will need a FEIN (employer identification number). You can get this online or by calling the IRS. If the LLC is your “alter ego” and you are the sole owner then you can use your own SSN (I think. You should pay for advice on setting up your company). But it might be better to get a FEIN for your new company anyway.
The bank account should have the name you are “doing business under”. So you can deposit checks made out to your “public” name.
If you want to do business as another name different from your LLC name (imagine your LLC is “RPK HOLDINGS 3 LLC”), you will probably need to file a DBA with the SOS. (“RPK HOLDINGS 3 d/b/a Manor Estates Country Living Park” This would presumably be sufficient to open a bank account in the name of the DBA. @jhutson says they’re county-specific. @Randy_CA says you don’t need a DBA. This is true if you can name your LLC what you want the park name to be.
I will not vouch for how it works in your state, because I have absolutely no idea what state you are in. You cannot expect to get good advice from random strangers on the internet.
You will also need to write down the “rules” of your LLC i.e. have an LLC agreement. Get a lawyer to help.
Finally, if you are changing the existing name then you should probably double-check with the local government (city, county) on how to do it even before you get the state formalities taken care of.