rear axle diy rebuild ??

[paj]

just recentlly replaced my rear axle on my mk6 transit because i lost drive to rear wheels ,i still have the old axle and dont really know whats wrong with it,all i did was take diff cover off and felt thru oil and found what i would describe as small metal teeth ,so i was wondereing is it poss to get and replace all parts? is it something i could do at home with own tools or do you need specialist ones?.would be nice to rebuild it to nearly .cheers