Is there any documents or could someone let me know how to update an extension dll?  i have some code that needs to be updated and have never compiled one before. 

Thanks@!

I recommend that you start with Technet and MSDN

How to: Create Management Agent Rules Extensions

Create Rules Extension

You need a compiler to compile your extensions. You probably need an IDE also. I recommend that you use Visual Studio to develop and compile your code (let it be C# or VB).

Visual Studio Resources

Thanks. I have VS 2008 installed, just need to know which file i need to open and how to compile/save it.

Without seeing your project or knowing whether it is C# or VB I'd say open the solution file (.sln) or project file (.csproj). The actual file you need to edit is .cs or .vb.

I know how to open the project file and modify it...what i don't know is how to save/compile it after the changes.  because it takes more than just click "save"...right?

I you have successfully opened the project in Visual Studio, you can right click on the solution and select 'Rebuild Solution' or press F6.

This will generate the assembly in the Debug or Release folder from the project's \bin directory.

If there is no post job that copies the dll to the FIM Extensions folder you will need to copy the dll manually, after you have updated the extension you can run a preview in FIM Sync to see if your change has the desired effect.