First of all, i would go back to the person giving you this order, as one week is more than "sportive".
First you should know at least a little about how is DNN working and how the pieces are playing together.
Second: you should have knowledge about VB, asp.net, a little HTML, CSS....all this things.....
Third: go
here, this is one of the best tutorials i've ever seen, and this is not said that i worked on it, too.
If you can skip 1 and 2, then it is possible in one week, depending on what you should build into DNN.
Honestly, i had the same problems like you. How the hack is this really (and i mean really) working? Reading some tutorials, hints, forum-entries.....i still had problems.
Then i found Johans page (in the link above) and we made the existing tutorial for vb. Now i know how the hack this is really working.
Good look anyway.
Cheers
Kai