First question "is it worth repairing" if it were mine I'd look to see what a new one is worth then divide that in half (cause that's what you might be able to buy a used one for) then figure about $120.00 for cleaning lubricating and adjusting the your lens. With your lens you know what you have, buying used might need the service. you are the one to decide. As for the second question "can I repair it myself" short answer no. If you have to ask if you can repair it then you don't have the necessary tools and general knowledge of how to dismantle and reassemble the lens (and have it work when finished). The lens took a hit and most likely set the inner and outer lens barrels out of alignment causing the inner barrel to slip out of its seal and or focusing gear and hang things up forcing it will break parts causing more repair costs. All else fails get an estimate before repair. Been there with a lens myself and after a couple a months without bit the bullet and had it repaired. Cheers best of luck