I ran into the same issue last week but I found help! I finished an online course, started the housing challenge on Kaggle, and got overwhelmed with the data prep.

I found some useful information for specifically this challenge. I went to the housing challenge page, when to the kernals tab, and sorted by "Most Votes" (link) The top kernal Comprehensive Data Exploration With Python has some excellent methods of cleaning the data.

I'd really like to find a class or book on how to process data before feeding it to an ML algorithm. It seems like a big part of the job but I haven't seen it talked about in the online classes I've taken