Wrx type RA jumps out of 2nd gear
 

It will not go in to 1st gear and goes in to second but when you let clucth up it jumps out have replaced gear box oil. Have been told that a 2lt sport gear box will fit is that right?

No you wont be able to replace it with a sports gearbox, it wont be up to the job and yours sounds knackered :(
Your options are to go to a gearbox speciallist, it may just be a couple of weak syncro's or you may need a full box rebuild, or you could go buy another wrx type ra gearbox, but like for like is always better!

Tony:)

hi mate im sure someone will be along soon to help you out lol
in the meantime i think you'll find the ratio's are different and your rear diff
should be the 4.444 ..... sport diffs are 3.9 better off getting the right box
mate ..... good luck on it though

what yr is it?? my 96 wrx ra has 3.9 diff....