No it spoils nothing. There are two wikis, a wiki of game of thrones and a wiki of ice and fire. Obviously the latter is about books, but the former is simply everything about the show and nothing more. I read it to cover the details that are easily missed while watching the show.
Plus I am a huge fan of the history of this GoT world and the details of the history, how all the houses came about, all the wars, etc, so I tend to read about the past a lot. I've been reading about Robert's Rebellion since the time I started watching the show, and I have hoped since then that they make a spin off or something to show that at least, if not the other awesome events like Aegon's Conquest.
I just want to see Rhaegar being cast in the show, everytime you listen about him from other characters in the show, they seem to be in awe and he is the one who started the downfall of Targaryens, he is one of the biggest characters in this world, plus if the Battle at the Trident is shown then we will see Robert in his prime. These events are faaaaaaaaaaaaaaar more interesting than the crap going on right now, if you ask me.
But this is all history and this only gets talked about in the show briefly, only when you have the likes of Barriston or some old git reminiscing about old days. Like that season 1 conversation between Robert, Jaime and Barriston about the time the Mad King got lost and this current chain of events started.