Embryodead is correct. to make the kind of changes you want you would have to be able to read and understand machine language (Binary), and use a decompiler, a hexidecimal editor, and compiler. All of these are ready available, but there are probably thousands of lines of code and unless you know exactly what you are looking for and are familiar with binary or ASCii code you may never find it, especially if the original coder was a sloppy and down and dirty code writer.
( which means the coding could be fragmented, and disorganise. Example: In line 2124 of the code, there is a reference for the machine to run a certain process composed of three lines of code. Those three lines of code could be anywhere within the 10,000 lines of could you are looking at. It could take you days or even weeks to find it. I know of only one person (personally) who can read machine language the way most of us read english. Anyone with this expertise is going to be extremely expensive to hire. Reverse engineering of code is a teadious time consuming proposition, and requires a great deal of skill.
What are his rates?