Is it feasible to use SDL2 to improve an existing game?

I work maintaining an old online game which I do not have access to the client source code. All modifications to the game client are made through binary patching.

I need to develop a feature to show helping tool tips in the game when certain conditions are met (eg. when the player’s character hit specific levels).

The first sketch of the feature is to (when the conditions are met) blur the game window and draw an (overlayed) image + text teaching the player about certain aspects of the game (something similar to what shift+tab does with Steam games).

As the working time is an very scarce resource, I want to know beforehand if this feature is feasible (and not too painful) to develop using the SDL 2 framework. Please consider that I do not have access to the application source code and everything needs to be done through reverse engineering, which makes some things much more challenging.

If you can also leave some basic guidelines on how to implement that using SDL 2 that would be very appreciated.

Thanks in advance!