scooby95wrx

hi ya all help if possible
took a partners uncle out for a blast in my 94 wrx.made a quick gear change into 3rd and one loud bang,pulled over could not get it out of gear to start with then i managed to drove back to his house in 1st with it making a horrible chattering noise.worked out that i can get all gears bar 3rd so drove it back home very steady,it has been crunching now and again more with quick changes into 3rd for a while,syncro maybe?would it be best to buy a second hand box or have this when repaired.

any one got any ideas
many thanks will