Sounds like the outer pane of glass just has a crack. So long as the fundamental layer of LCD isn't compromised and bleeding, I'd seriously leave it alone. IF you're determined to get it fixed I would say do it legit.
The non legit is trying yourself--it may be a "can of worms". I've only ever succeeded in replacing batteries in 2nd gen nanos and similar. Also such a thing needs a good set of precision screwdrivers, a little real experience and knowledge so you know what you're doing, an antistatic wrist strap with good grounding (don't want a stray ZAP to fry anything), steady hands, and obviously a reliable source for replacement parts. Maybe support of nerds who physically hack items such as ipods found on blogs and forums.
Even so, success is far from guaranteed. You'll save money but is it worth the risk?
I should qualify myself: people have dumped off their ipods on me so I've had a few to practice or experiment on. Shaky proposition at best.
We'll murder them all, amid laughter and merriment...except for the few we take home to experiment!
"I cant see S***! --YOU GO TO HELL!" --Tourettes guy