In Congo you will find mostly Let 410 and you need the rating if you want to be sure to find a job.
I know of a girl who went to Congo and found a job quickly because she was there to start the next day. Also she told me that the maintenance of the aircrafts in Congo is pretty much poor. So you might consider this too, before jumping into the first plane to Kinsasha.
The same old story, you won't get answers on emails. Show up and maybe you get something. Age doesn't really matter.
Here's a list of operators out of N'Dolo Airport, there are some more from other airports, but I have no info on those: