If you are operating in windows (which I am going to assume you are) you can use the inspect.exe tool that comes along with visual studio. It will allow you to interact with the dialogue box and even send any information that you want accurately including selecting elements from the drop down or any other interaction needed. This even works if you wish to save files using selenium, but to answer your question, you can even use it to detect if that window is indeed there. How you want to proceed from there is your call.
//using System.Windows.Automation;
//using System.Windows.Forms;
AutomationElement desktop = AutomationElement.RootElement;
AutomationElement Firefox = desktop.FindFirst(TreeScope.Children, new PropertyCondition(AutomationElement.ClassNameProperty, "MozillaWindowClass"));
AutomationElement PrinterComboBox = PrintForm1.FindFirst(TreeScope.Descendants, new PropertyCondition(AutomationElement.AutomationIdProperty, "1139"));
SelectionPattern selectPrinterComboBox = (SelectionPattern)PrinterComboBox.GetCurrentPattern(SelectionPattern.Pattern);
AutomationElement ItemInDropdown = PrinterComboBox.FindFirst(TreeScope.Descendants, new PropertyCondition(AutomationElement.NameProperty, "SelectPrintMethod"));
SelectionItemPattern ItemInDropdownSelectItem = (SelectionItemPattern)ItemInDropdown.GetCurrentPattern(SelectionItemPattern.Pattern);
ItemInDropdownSelectItem.Select();
AutomationElement OKButton = PrintForm1.FindFirst(TreeScope.Children, new PropertyCondition(AutomationElement.AutomationIdProperty, "1"));
InvokePattern ClickOK = (InvokePattern)OKButton.GetCurrentPattern(InvokePattern.Pattern);
ClickOK.Invoke();