Not sure if that guide is what you want in terms of flashing the 7020. You can use the null cable method, but most people use the Web interface method to flash, its simplest and probably quickest. I have done a dozen flashes this way, and the only problems seem a dodgy image from Hyrda. A guide I found somewhere, slightly modified.
1- Hard reset box, or turn off at back.
2- Switch on the dreambox while holding the front panel lower button (Lower Channel Button).
3- Keep holding till ( *** STOP *** ) appears with the IP of your box just above it.
4- Now you are ready to upload a new flash image.
5- Open you browser and put the address : http://(box ip)
6- Click firmware down the bottom, chose your firmware, and press ok.
7- It will then upload your firmware to the box and flash it all automatically. Once updated it will say finished. Then simply reset your box!
Note: Probably best to use opera, firefox, something like that. I use opera, it tells you the progress of the uploading unlike IE which is handy.
Also you want to setup your networking first before you do this, make sure that works fine, test it, etc.
Recommended...Gemini image. I have tried them all for the 7020S. Hydra never worked for me, although it is suppose to be good. Gemini however in my opinion is excellent. Still supported by the authors, excellent PC side sofware, you wont be dissappointed.