As a general note because people tend to confuse this:
Obviously, many written texts use the Präteritum, even though one gets the impression that it is scarcely used in everyday life. Now, this does not imply that Präteritum is the past tense used in written form whereas Perfekt is the kind of informal spoken form of it. Nor does it mean that one needs to convert a spoken Perfekt to Präteritum when writing it or use Perfect when re-telling a scary novel at a campfire.
Obviously, there is a point to it or people wouldn’t notice. However, it is of course not that Präteritum was so complicated that it could only be used at a desk with one hand in the conjugation table.
The reason is that the form and intention of texts which are written down and texts which are spoken differs:
Präteritum is the way of telling a story. Therefore, it is also used when writing a story. A story in that sense is anything which is remote. It may be in the past, it may be in the future, it may just not be of primary concern for the person who tells it.
Perfekt is the way of discussing something which happened in the past and is of primary and immediate relevance for the person who tells it. So, when a friend asks, why you look so happy and whether any of the events the other day are related to that, you may very well use Perfekt tense because it is not remote to you or him/her.
As an interesting read, I may suggest the book ‘Tempus: Besprochene und erzählte Welt’ written by Harald Weinrich which explains this difference for various European languages. (I think the belleslettres article makes similar arguments but I haven’t had the time to fully read it.)