I had my sdi octavia on the ramps today when i took the engine cover off underneath There seemed to be gearbox oil leaking from the driveshaft.Is this a big problem and can it be fix easy?

Oil leak fromthe drive shaft suggests you will need to change some seals. I take it the filler bolt on the box is done up ok and it isn't just leaking onto the drive shaft.

there's a seal which looks like this behind the drive flange.... it's quite dificult to change the seal without damaging it

The leak is coming from the other side of the fill plug.Is it a garage job or could it be done by me?I mean does it need any special tools?

See toms comment

Unless you are pretty good with the tools, I'd say garage job.

yeah garage job i'd say..... that is of course it is actually the seal leaking....

undo nut on end of drive shaft, split ball joint, six bolt to undo on drive shaft, remove drive shaft, undo drive flange bolt(they are f-ing tight), remove seal, fit new, re-assemble........ easy peasy