Can't get past lvl 25 … Mission!

you’ve come just to the right place as we are no server community but a pure modding community and therefore only hide information on cheating involving abuse of the server and client software via the world wide web.
the best resources here are the starport archive and the wiki. our downloads are numerous but if searching for the right keywords you prolly will be directed to what you need.
the save file format is not different from any other ini file format while the parameters are clearly more obvious than in some of the other files. to open up a save with the save editor you have to have the save editor executed and than go to file - open and select the save file you need. the save files are stored in your document\my games\freelancer\accts\ direction and the save editor only works with the single player saves as multiplayer saves are not encrypted and can be opened with any simple text editor. keep in mind, that multiplayer savegames are the ones you recieve from players who join your machine’s server if you offer one.
there is a way to understand the savegames (*.fl) file name, can’t help you with that but if you look on the last change date and time you may come to the very save you are searching for.

Did you install the official patch, after having played without? The internal mission numbers changed, preventing levelling up. It can be fixed by searching for MissionNum and adding one to it (41 becomes 42). If MissonNum is already 42, or you’re not using the patch, I don’t know why you can’t increase level.