No 3rd, 4th gear in my auto tranny!!!!!!!!!!!!!!!!!!!!

[Protege-Fiend]

so ive been avoiding posting this because, i feel like a dumb ass knowing its not so good for my vehicle and doing it any way just because its my only mode of transportation. Any way i cant remember how long ago it happened, im assuming around the end of summer into winter, but any way my transmission started pooping out on me one gear at a time, started off with 4th acting really hesitant and like it had a lack of power then..... poof it was gone and i only had 1st, 2nd, and finally 3rd, and at the time i was really strapped for cash and was going to attempt to ride it out until summer...... which it ended up not going so well because 3rd gear started doing the same thing and then it also s*** out and now im stuck today with 1st, and 2nd only! Oh and if it wasnt made clearly ive been driving the car every day ever since the gears started crapping out and on a reg. basis when im driving around down i usually do 40-45 miles and hour and thats at about 4,000 on my rpm's but i was blessed and found a parts car same hear and every thing with 45,--- odd miles and its a 4 speed auto. this is were my question really comes in since ive been driving my car for so long with only second gear would i be better off swapping the motor and transmission out of the other car or, would it be safe to just yank the tranny from the parts car and just stick it to my motor. i need any kind of suggestion as fast as any one can give any because i live in alaska and -10 to -45 is really cold weather and im surr its helping my tranny die even faster so any kind of words of wisdom would be greatly appreciated!!