The tracing isn't that difficult. The best is to trace from the original before you resized it to that size.

Cheers.

Learn up the Adobe Illustrator Pen Tool..

http://www.2ginc.com/tutorials/illus02.html

After you've done the tutorial and know how to control the Pen Tool averagely well, then do follow these steps.

1. File > Place (import the image file you want to trace.)
2. Double+Click the layer with the image and Check 'Dim images to 50%'.
3. Lock the layer with the image file.
4. Create a new layer above the layer with the image.
5. Start using the Pen Tool and trace.

The Pen Tool requires patience in learning but once you've got it, it's very handy especially in Illustrator.