I used to rip em apart, but I stick to RAM upgrades now! The old eyes are going! My iMac 27" i7 has 16GB of RAM (Came with 8) and I did that myself, but I have Applecare on all my stuff.
Your best bet is to find a local computer shop, ring them and see if they know what they are talking about....SSD? If they sound okay, look for recommends in your area....Best I can do I'm afraid.