One tool I can think of is tdump.exe from Borland, but I don't thing you get the full function details from it. Anyway, you can download at **broken link removed**
There are other tools that extract the full information, but will only work with VB DLLs, or other specialized DLLs.
In order to proceed with a debugger, load in the debugger the program that uses the DLL, and trap the calls to the function names (which you may learn by using tdump). Once you break on a function call, you can try and guess what are the parameters from looking at what is pushed on the stack, but you may of course be wrong.
As a debugger I recommend SoftICE, but other debuggers will do as well.