Dying an Ugg Leather Purse -- deglazer, color prep, which brand -- HELP!!!

[Shopperaddictgirl]

I have an Ugg crossbody bag that I would like to dye a darker color in the brown family (my bag style on the left, color of my bag in right picture).  I have NO idea how to do this. I bought Fiebing leather dye in 'dark brown'.  I would like my bag to come out similar to the color in the left picture.  My choices of dyes were 'saddle tan' and 'dark brown'.

I know I am supposed to prep the bag first....but how?  I have read about Fiebing 'deglazer' and Mltonian 'Nu-Life Color Preparer'.  Please point me in the right direction of how to darken this bag and not ruin it 

Thank you for your help!

[Halitech]

chances are, you won't be changing the color, at least not to the color you want. usually most commercially available products use chrome tanned leather which is dyed at the time or tanning and then finished to prevent color change. you could try the deglazer in a small area that is not noticeable and then dye it but I'd be surprised if it works

[Shopperaddictgirl]

Thank you for your response 

[Shopperaddictgirl]

So....in your expertise opinions:

1.  This IS doable?

2.  Will NOT ruin the bag?

3.  WILL produce the darker leather I would like to achieve?