Nothing wrong with wanting to save a few bucks. I've bought parts from ebay and been quite happy with them. That said, I'm totally relying on the manufacturers warrantee now for them. Buying from a store (physical or online) gives you that return policy, as well as manufacturers warrantee. Ebay, if it breaks, you are stuck, if it is DOA (unless you get lucky) you are stuck. Its most definitely buyer beware. Is it safe? that's up to you really, depends on what people you are getting the parts from, are they large sellers, have good reps, read the reviews etc. Try not to get parts from companies overseas, stick to US soil, may cost a hair more, but someone here is selling it, so you have some recourse. You have done your homework on the parts, now you'll have to take one step further, do some reading on who is selling.
Only other thing to say, is good luck with your shopping, and hope everything turns out great for you.