Amd radeon 7470 1gb
I know that this is old but i have very low budget
What are the risks? You could damage the processor. You could damage the motherboard. If you are careful and you properly ground yourself while doing the replacement, it is fairly straight forward.
Going from a Conroe E6550 to a Wolfdale E8400 is really not much of an upgrade. Can you return or exchange this E8400 that you purchased? You should get one of the (quad core) Yorkfield processors (Q8200, Q8200S, Q8300, Q8400, Q8400S, Q9300, Q9400, Q9400S, Q9450, Q9500, Q9505, Q9505S, Q9550, Q9550S, Q9650, QX9650 or QX9770).