When I ferment in a corny keg I neither remove the gas in dip tube nor the guts of the gas in disconnect.
You can just attach the gas disconnect to the keg and attach some tubing to the disconnect (put the other end of the tubing into a jar of sanitizer).
If you are only fermenting 10 liters in a 5 gallon keg, you shouldn't have any issues with blowoff. The gas will vent through the disconnect.
And if I want to collect the yeast, can I simply do this by means of forcing CO2 through the keg after primary fermentation, and collect the first few messy pints?
If you build a jumper cable, you can use CO2 to rack beer from the fermentor keg into your serving keg. Some yeast and other trub near the bottom of the liquid out tube will come out first, and you'll want to direct that into another vessel before redirecting the flow into the serving keg.
In my experience, the majority of the yeast, etc. will remain in the fermentor keg until you get down to the last bit of beer.
There is some good info and instructions here: http://www.thebeerjournals.com/Racking.html