HOW-TO: Compile Custom Kernel Modules

I still running in to some errors when i'm trying to compile the desired modules...
I have a ReadyNas RN102, with firmware 6.1.8.

I want to compile the usb serial driver modules:
- PL2023
- Generic Serial

I did al the above instructions, accept:
- I copied this file /linux-3.0.101-0.15/arch/arm/configs/armada370_nas_defconfig to /linux-3.0.101-0.15/.config
- Then I ran menuconfig, and enabled the modules.
- Followed by make arch=arm

Then I receive the following error:
make: arm-mv7-linux-gnueabi-gcc: Command not found

This must have something to do with cross-compiling. But as far as I know, I don't want to crosscompile, because i'm compiling on the machine.

I tried to edit te .config file. Commented the line: #CONFIG_CROSS_COMPILE="arm-mv7-linux-gnueabi-"
Then its starts compile, but in the end I see a lot of errors and can't find my modules...

Any help would be appreciated!