Try learning just a few riffs at a time. Then you can procede faster. If you try learning the whole song at once, it will be near impossible. Get out the CD/Tape/MP3 or whatever and start with the first 10 seconds and try to get that down pat, then move on another 10 seconds, so on and so forth. Pretty soon you'll have it.

*Side note*
One of my buddies, who can shred like hell, learned that song and it took him about 4-5 months to learn it completely.