Do not preheat nozzle before loading filament to MMU in first layer calibration wizard.

Show insert PLA filament to the first tube of MMU instead of "to the extruder".

First layer calibration wizard with MMU is now functional. But there is no option to unload filament from wizard.

Firmware/ultralcd.cpp

@@ -4373,8 +4373,11 @@ void lcd_wizard(int state) {
 			    wizard_event = lcd_show_fullscreen_message_yes_no_and_wait_P(_i("Is filament loaded?"), false);////MSG_WIZARD_FILAMENT_LOADED c=20 r=2
 			}
 			if (wizard_event) state = 8;
-			else state = 6;
-
+			else
+			{
+			    if(mmu_enabled) state = 7;
+			    else state = 6;
+			}
 			break;
 		case 6: //waiting for preheat nozzle for PLA;
 #ifndef SNMM
@@ -4399,7 +4402,13 @@ void lcd_wizard(int state) {
 			state = 7;
 			break;
 		case 7: //load filament 
-			lcd_show_fullscreen_message_and_wait_P(_i("Please insert PLA filament to the extruder, then press knob to load it."));////MSG_WIZARD_LOAD_FILAMENT c=20 r=8
+		    if (mmu_enabled)
+		    {
+		        lcd_show_fullscreen_message_and_wait_P(_i("Please insert PLA filament to the first tube of MMU, then press the knob to load it."));////c=20 r=8
+		    } else
+		    {
+			    lcd_show_fullscreen_message_and_wait_P(_i("Please insert PLA filament to the extruder, then press knob to load it."));////MSG_WIZARD_LOAD_FILAMENT c=20 r=8
+		    }
 			lcd_update_enable(false);
 			lcd_clear();
 			lcd_puts_at_P(0, 2, _T(MSG_LOADING_FILAMENT));