fitte23 , i would not recommend you upgrading your firmware. You will most likely kill your player instantly.
However, i'll suggest that you backup your firmware with the S1fwx tool. The guide is here
http://www.mympxplayer.org/how-to-ex...tool-vt66.html
Also, you can theme your player. The guide is here
http://www.mympxplayer.org/how-to-mo...ng-vt1719.html
But always ensure that you use your own extracted firmware for theming.