Hi Jhong, the method I used was hit and miss as I had never done this before. Here goes the condensed version of what I did.
First, in PS CS5 I made several copies of the image to save time undoing approaches that didn't work so well.
Next, I took a sample of the color right beside the part of the watermark I was working on and at 500% zoom, I used a 1 pixel brush (based on the sixe of the text) to paint over the text. This blended the text with the background so that it was barely seen.
Now I could use the Spot Healing Brust and Clone Stamp tools to blend the adjacent colors and textures over the remaining shadow of the text.
Once the text was gone, I blended back in from the original, any area changed by the retouching tools that were close to where the text was.
Going back to the retouching tools I could do very minor adjustments in the area where the text had been because now the image was identical to the original right up to that point.
Lastly, I touched up anything that was obviously changed. For example, I used a 1 pixel brush to redraw the portion of the hair that ran across her neck that the retouching tools removed.
The process took about an hour. I'm guessing that there are tutorials on-line that are much easier and faster but my goal was to experiment and learn and I didn't mind at all looking at the lovely lady for an hour!
Hope this helps!