Don’t need to buy the spare parts, keep your money, buy a can of "white grease" from CT, spray the gear once a year, then your opener can last forever,
However, check your door "counter balance spring".
Thing to do--> pull the emergence release rope from the garage opener, let the door free from the carrier shuttle, open the door by hand few time. Let it stay open half way. If the door is too heavy to open, or door do not stay wherever you stop. It mean the counter balance is out. (This is the reason why the gear is worn out, the door was to heavy to move. the motor and gear did the hard work.
The counter balance has "Stored Energy” DO NOT DIY to adjust it. Lubrcate the gear will help reduce the wear and tear on the gear.