Hi Les, I have attached link to 3 drawings. Max7219 pinout, 5 digit 7 segment display and Matrix board pinout. The top corner of the Max7219 chip with the little dot is pin #1, you can verify this by metering between the chip pin and the Din connector on the board. Now for the connections to the 7 segment display you will need to verify the pins from the Max7219 to their locations, if you look at the picture of my board, you will see which pin is connected back to the Max Chip. Yours may be the same but you need to verify with meter between the pin on the Max Chip and the board pin, that way you can then set up the proper wiring. The 5 digit 7 segment display drawing I attached is from my displays, now you have a 6th digit so if you don't have the proper pin locations on your display this will take trial and error. Another thing I found is that there doesn't seem to be any standard in labeling of the Dig input pins, you will notice that I have renumbered mine in my drawing as they were backwards. Note that Dig 0 will be the right most segment of your display regardless what they have labeled the drawing. So in my example Dig 0 (pin 2 on Max 7219) goes to Pin 8 on my 7 segment display, Dig 1 (pin 11 on Max 7219) goes to Pin 6 on my 7 segment display and so on. If you assign pin 30 on the ATMega to Boeing 737 airspeed, you can use the speed setting to check for proper segment wiring as you can vary all the segments as the numbers go up by one. Once you find one of the Dig inputs you can verify the A,B,C,D,E,F,G segments are correct by varying the numbers and making sure the correct segments are lit. After that the remaining pins will be the other Dig inputs and just try them one at a time till you find the right order. Record your findings as they will always stay the same, and no you don't need a resistor for this to work.
Cheers, feel free to contact me if you have any further problems
Also just verify that your CS pin is connected to pin#27 on the ATMEGA board and DIN is connected to Pin #28 couldn't be sure from the picture.