I would find someone to do it for you cause if you don't get the dump just right and don't verify it your ps3 will be lost forever. But if you do decide to do it yourself send me the link to your dump and I will verify for it and make sure it is good before you write anything back to the ps3.
Also the e3 will only work on nor ps3s, it will not work on anything other then those. If you have a nand ps3 you will need the progskeet or the teensy as the e3 doesn't write to these systems. Thanks.
So it comes down to model numbers. If you have Cecha01 to cechg01 it is a nand. Anything else it is a nor ps3. Also if it is a 3000 or a 4000 model it can't be downgraded. Run this to see if it can be downgraded.