A complex thematic that could not awnserd within a short posting. What you need is a longer search and some talking sessions with other users. Explore the projects ( Discord Groups) to see some ideas and to talk to the creators.
1. Gauges vs. Screen
Building lots of Gauges in a small area is advanced, expensive and finally difficult to handle. For sure possible but this is not a beginners work. And i would say without CNC your out of buisness here. May you find a shop for C172 Gauges.... But i will say 99,9% you find nothing for a JU52. So "Self Build" is a must have here.
So lets talk about the alternate..... Called "Airmanger" or other programms in this logic.
This Software get Data from the Sim and can show the "Gauge Disc" ( E.g. the label and the Needle of the SpeedMeter). You can put this "Window" on every spot on your screen and you can resize it as you need. So logic is.... You Buy a Wood/Acryl Plate.... Paint it and you cut "just" the round holes for every gauge you need. Then you mount a screen behind the plate..... And you finally create all the gauges as virtual Windows on that screen and move them to the spot you need.... So the "Picture" is directly behind the drilled hole in the plate.
Check THIS...... https://cessna172sim.allanglen.com/docs/instrument-panel/
If you decide for real gauges......
2. What Motor.... Here i will say Stepper. Servo workes but is not so perfect and accurate. And Steppers allow "over360" instead of Servo.
Technical you should plan for a external power to the motors..... So they are controlled via Mega ( ULN2002 Boards) But they are powerd from a 5v supply external !
Steppers need a lot of power.... So already 2 Motors would overdrive the Mega Limits !
3 Constructing without CNC
Difficult. Whatver you should not think about "Housings".
Techical the front side of the gauge can be a quadratic Acryl Plate 2-3mm painted. One hole in the middle for the shaft. The Motor is behind. You finally screw this element from behind on the Front Panel that have a cuted round hole.
Basically you not need to take care how the panle looks from behind. The front must be realistic. All other not matters.
So i would not think about Gauges like oin real ( A Round Zylinder including all the Mechanic and is put into the Hole from the front) . You can "fake" here by putting a round frame on the front so it looks like the gauge is located there..... But in real its just a quadratic plate on the other side.
I will say lots of things are possible. You can cut the round holes by put a bottle of beer on the plate and mark the frame with a pen and then cut it with a hand saw. But to be realistic..... If you like a "perfect" Look and a realistic feeling then you will need CNC at the end.
Search the web and talk to other people. May you find a friendly user near your location who got a CNC and can help.
Also some factorys have a CNC for there work and may you can talk to them and for some bucks and a little gift they can support you. Finally there exist Websites you can order perfect CNC Panels on your own CAD Files. Not cheap but perfect. Specialy CHINA is currently cheap and fast !
Simply ask if you got specific questions !