Creality switch to a short shaft motor around 2020.
No idea why you think returning the printer 3 times was the right thing to do here. Throwing the baby out with the bathwater.
Yes, you should buy a new extruder motor. I'm guessing the gears you want to use have screws. If so get a motor with a flat side so the screw is seated fully. This should work: https://www.amazon.com/dp/B091CXPXVP/ref=cm_sw_r_apan_glt_i_XJXZS3CXK08AE8RXNQGM?_encoding=UTF8&psc=1
This is what I used. I printed it and used a bolt and nut and pressed it out.
The issue you are going to run into is, because the shaft on that motor is short, most all extruder "kits" are not going to work. They are usually made for longer shafts on the stepper.
You could just get a new stepper and keep that one as a spare. I bought this one.
This isn't the same link as what I bought, but it's the same motor: https://www.amazon.com/Creality-Printer-Stepper-Extruder-Compatible/dp/B091CXPXVP
Any 42-40 motor with a shaft around this length should work. If you want to put a knob on the extruder, you need an even longer motor shaft since this one is flush with the top of the gear.
I have the micro swiss all metal dd setup. I will just say it's night and day the quality it produces. I have my retraction set to 2.5mm and have no stringing. I still run 80mm/s and on a test cube there is some ringing and ghosting, but on a normal print that has contours like a bust or figure it's running absolutely flawless. I will say however. Check your extruder motor before you pull the trigger on it. Make sure it's not a pressfit gear on it. if you have the D shaped shaft with a set screw your golden. if not you can get a 42-40 creality replacement for like $18 on amazon https://www.amazon.com/gp/product/B091CXPXVP/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1 That's the one I got and it worked perfect out of the box. I did have to update my steps on the extruder. which is a bit of a pain. But once you do it you'll never have to worry about it again.
This is the one I got. The reviews say it works for the micro swiss upgrade
If you buy the silver extruder, the one that says creality on it you won't need a new motor, it's the same extruder you currently have but made out of aluminium.
The other two extruders are dual gear ones so the silver wheel is replaced by a second golden gear which grips the filament on both sides.
This is the motor is anyone that says 42-40, this is the official creality one:
And this is the exact same thing for cheaper:
its a press fit.
either you get yourself a puley puller that fits, or you cut it off ( make sure no dust gets into the stepper )
after that you need to grind down the shaft n one side ( to make it a D shape ) so the grubscrew of the new gear has something to push against.
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most just buy a new stepper that has a D shaft... ( https://www.amazon.de/Creality-Schrittmotor-3D-Drucker-Extruder-Kompatibel/dp/B091CXPXVP/ref=sr_1_7?keywords=ender+3+extruder+stepper&qid=1640717339&sprefix=ender+3+extruder+ste%2Caps%2C80&sr=8-7 )
you can get one on amazon for like 20$ you will want a 42-40 stepper motor with a D shaft. like this one
https://www.amazon.ca/gp/product/B091CXPXVP/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1
only thing is you will need to get another gear as the one you have wont work for this motor but you can always upgrade to a dual gear extruder top like this one