Hi,
IDA is superb tool! And, you can get the x86 instruction set here:
*home.comcast.net/~fbui/intel.html
*www.intel.com/products/processor/manuals/
And, you may want to take a look at this very good book too
*www.amazon.com/Hacker-Disassembling-Uncovered-Kris-Kaspersky/dp/1931769222
It has some good info about debuggers, disassemblers, identifying higher-level programming constructs like loops, branches etc among other things.