Alright, here is the skinny. You pretty much have 3 choices: Apple, iFixit/similar, or eBay. Apple will charge so much that you will just have to buy a newer model. Many people do this, and get, say a new 13" MBP or Air instead of the 15" they are used to. iFixit, Powerbookmedic, and some others are good what they do, have long warranties, and are expensive. eBay sellers are often not so good, have shorter or no warranties, but are cheaper. In the end you have to choose. I run a one-man Mac repair shop in Santa Fe (don't worry I won't promote it), and once I have narrowed down where a part can be found, I will offer my customers the choice of, typically, a higher-priced repair with the matching warranty from iFixit or similar, or a lower-priced repair with a part I found on eBay, with a shorter warranty. Almost always, they will choose the eBay part and save, quite often, a few hundred dollars.
One thing I will say, eBay has improved drastically on the returns side. In terms of returns and refunds, I have had 0 problems of, I don't know, 200 things I have bought there since about 2012. Before that, this was not the case. They have come to strongly favor the buyer in any given situation.
I will usually "vet" a seller on eBay by asking them a few questions, and make sure they know something about what they are doing, and aren't just ripping parts out of Macs and reselling them. Actually, this is exactly what iFixit does, but they at least have some knowledge and good customer service. I will then bookmark the sellers I trust and browse them for parts when I have a repair to perform. The best recent one I have discovered is iPros, they are at
http://stores.ebay.com/ipros
I mention them specifically because I see they have your board on sale. They used to have like 1000+ feedback, I wonder if they changed accounts or something? In any case, I have bought 3 logic boards from them, and they have all arrived in water-proof, ESD-proof, double-sealed packaging, which so far is unique to them. I personally give a 90-day warranty for repairs, which is almost matched by their 60-day one. They should change it to 90 days, as most decent shops will offer that or longer.
In any case, you are talking about hundreds of dollars upfront and then, in your case, performing the repair yourself, which can be a little scary if you are new. Just make sure to at least get a wrist strap. Probably radioshack or similar, or, again, eBay - there are some generic ones on there for a dollar or two.
If, on the off-off-chance you are in Santa Fe, I would do this for you, but even then, I see you are trying to save some money. Just be careful and take your time. Good luck!
