Working visa after an overstay as a tourist - Medellin

Hello everybody,
The last day of my tourist visa will be this 30th June. Indeed It will be 180 days I'm in Colombia as a tourist in 2017. My plan is to stay here and to work as a French teacher in Medellin. The last few weeks I had some interviews which went well but for some reasons beyond my control, I need to wait a few weeks more before getting my working contract. I am in contact with a visa broker organization in Medellin called Inter-Col who will take care of all the paper works for me. Inter-Col told me that the fact I will be overstay for a few weeks won't be an issue for my working visa as soon as I pay the fine (400000 pesos por 1 month If I'm right?). They also told me that I need to wait to ask for a Salvoconducto because I need documents such as a working contract or at least a letter telling that the school want to hire me.
So I would like to know if some of you guys has been in the same situation as me and confirm me that:
1) An overstay of a few weeks won't be an issue to get my working visa afterwards?
2) Do I really need to wait for a working contract or a letter telling that the school want to hire me  before asking for a Salvoconducto? Or can I go without it in order to not be overstay?
3) Last question: Which others documents I need to have for asking a Salvoconducto?
Inter-Col seems to be a serious organization but It's always better to double check with people who has been in the same situation as me ;-) So guys, if you have any relevants informations or feedbacks, please share It with me!! Thanks in advance ;-)