Driver shaft issue

What is your question?

I took the wheel off and the rod that goes up to the engine thru the tire and holds all the pieces of the tire on (a huge thick rod about 1 inch circumference completely is broken in two. I went to Advance Auto and they sold me a drive shaft for the front drivers side. My brother said he would try to install for me (I have no money). I guess my main question is there anything I need to tell him that is very important for him to know when installing, anything he could do wrong that could make the problem worse or anything he needs to make sure he does so the next time I drive my car with my 10 month old so we both don't die suddenly??!!?? Thanks for anyone who can give some (any) advice!!! Jenn