So similar to German.
Only in German, the g sounding like "ch/k" only happens when it's at the end of a word (and even then it's pretty regional). Of course, v straight up sounds like "f".
Is this the general pronunciation regardless of where the consonants are located?
To me, it doesn't sound at all like the German "ch" (as in "ich"). That is a sound made with the top of the tongue at the front of the mouth just above the teeth - for the Dutch "g", the tongue is further back in the mouth, and the sound is a lot harder.
I read a good description of it as being like the Spanish "j", and the altusvantonder's comparison with the Scottish "loch" sound is also a good one.
The dutch 'g', to me, is what linguists term a 'velar fricative', which on the International phonetics alphabet (IPA) chart, is /x/. Here is a link for you to listen and tell me if I'm right :) http://web.uvic.ca/ling/resources/ipa/charts/IPAlab/IPAlab.htm
also, I would say the location of this sound is a non-nasalised 'ng' sound, if that helps at all.
I would say you can pronounce the -en when you are leaning to speak Dutch. In the official standardised form of Dutch (called "Standaardnederlands" or "Algemeen Nederlands") used on TV and other public channels, you would pronounce the -en. However, in normal speaking amongst Dutch people, even in formal settings, it is very common to drop the "n" at the end of words. So there is no right or wrong way of pronunciation, but learning the standard forms first and then progressing to the more nuanced differences is probably easier.
Not really. In Dutch we say 'goedemorgend' in the morning, 'goedemiddag' in the afternoon, 'goedenavond' in the evening and 'goedenacht' in the night or before going to bed in the evening.
'Goede namiddag' will be understood, but it is not a normal way to speak. 'Goedenamiddag' as one word does not exist.