You'll miss a few nods here and there but overall you're good.
You don't really need to be a Metal Gear fan to enjoy the story.
Besides, the best bits of the plot are entirely unrelated to Metal Gear canon.*coughcoughARMSTRONGcough*
Not really, it's quite a self-contained story. You will be getting a lot of spoilers for MGS4 though, if that matters.
Ah k. Thats good then. Get the feeling I should probably play the rest just because of how amazing everyone says they are lol. Looks like that huge Legacy collection just came out in Australia too...