zerothread/168578
idk if this will help, but this was in the tutorials forum and it shows you how to get the transmission out of a 240sx. i would guess that it would be fairly similiar. this tutorial will show you how to remove the transmission and then replace the clutch and flywheel. you can stop after you using the tutorial after you have got the transmission off, but i would highly suggest putting in a new clutch and flywheel. the diff. is day and night. i hope this helps, sorry i dont know much bout the sentra's. but good luck with all the work. post some pics of the body damage so people can see your progress and you can get some cool feedback!!! Good luck man!
ps.. i have to replace my clutch and flywheel this friday. my clutch just recently went out on me!!!