Reverse engineering

I want to do some reverse engineering but my knowledge is rather limited. I'm working on Windows.

To be precise, I want to reverse-engineer a protocol used by a flash application, but I can't just sniff packets as the connection is encrypted.

So I thought that perhaps I could "hot patch" the functions that encrypt/decrypt the data sent/received so that they would save the data in a file, which I could then analyze.
But I'm not sure what to do now. I know how to use OllyDBG to attach to the process I'd want to infiltrate and check the modules it imports and the functions imported/exported by the modules, but I don't know how to (easily) check which of those functions are called, and then I would have to change the code of those functions, which I've never done before, and I don't even know if I should prepare a second DLL to replace the original one or simply change the functions directly in the memory of the process I'm targeting.
Or maybe I'm overthinking all this and there's no need to mess around with WinAPI stuff and I could exploit the fact that the protocol is used by a flash application.

flash application
one word, SWF DECOMPILER, thread over.

>>6,10
Using native tools for this is as productive as trying to debug a Java application by tracing through the JVM.

>>11
I haven't noticed that he was talking about Flash. There are some specialized Flash disassemblers/assemblers/deobfuscators and even emulators/JITs, besides Sourcetec's decompiler (which doesn't always generate valid code). Unfortunately I don't think I know any debuggers, in which case you will have to resort to native debugging: I've done it multiple times, especially when digging undocumented Flash stuff or when hooking certain Flash function calls - why mess with complicated permissions when you can just grab everything you need from Flash's DLL memory (the only problem is that it's written in SEPPLES and it's filled with indirection making it a pain to understand, but give it a few hours and you'll get familiar with the code).