Last week i bought my first wrangler, a 99 sport with a 5 speed, i am fairly new to driving stick, but i am also pretty good at it, but the 3rd time that i was out driving it since i got it i noticed a burning smell (from reading other threads i'm thinking it is the clutch) (i'm also 18 and fairly new to cars)then the check engine light came on and it ended up being the O2 sensor. i told my dad about it and he said not to worry and be careful. i drove it 6 other times since then and 4 out of the times the burning smell came back. Also the last 3 times of those 6 i had some problems shifting into 4th and 5th gear. so tonight i was changing the O2 sensor and oil, and i wanted to drive it around and see if the light went out and i started having trouble shifting into 3rd, so i got it home then my dad wanted to drive it around to make sure there was something wrong and it wasn't me. well we pulled out of my driveway then onto the main road then when my dad went to put it into 2nd i wouldn't go. we turned down the next street and we stopped. it wouldn't go into gear, we were there for 10 min trying to get it into gear, i ended up having to push it and we were finally ably to get it into first, we were able to get it home and i don't know what happened.
Can someone please tell me what might have happened i think its either the clutch or the transmission but i don't know how to check, any tips would be helpful.