I do wonder how people coped without Google. Like you the vast majority of my skills (Excel and now SAP) have come from jumping in getting my hands dirty and an awful lot of Googling.
Training courses while useful, never quite replicate what you learn when you have to pick something up and...
Did you put a = at the beginning? so =SUM(...
The = at the beginning indicates its a formula rather than just text.
Still think mine is simpler because it doesn't require ctrl + shift + enter at the same time to turn it into an array forumula:
=sumproduct(value(substitute(a2:a4,"*","")))
My previous sumproduct solution could be switched to SUM(VALUE(SUBSTITUTE(A2:A4,"*",""))) if using an array formula. I find sumproduct slightly easier as I often forget the key combo to enter an array formula, though not nearly as frequently as I forget how to enter a new line in the text box!