1990 trasmission shifting issue + smells burnt

1990 pathfinderr automatic. :runaround: the tranny acts up when shifting...I went off roading and since then it acts up when i drive it. won't shift to 3rd or 4th or just revs up...anyway i checked the fluid, it was low, i added addictive, and now i checked it after a short trip and ATF smells burnt...is my tranny cooked and $$$$ is needed or it is just a simple tranny service?