I have purchased tickets throught ebay and will receive through email?
Can this be legally done? How do I know if the stadium will accept
this emailed ticket?

If the tickets you purchased were from Ticketmaster then they are
probably 'Ticketfast' tickets. These tickets will have a bar code on
them. When you get to the event, the ticket taker will scan the bar
code. If the bar code hasn't been used already, then you'll get in no
problem. These types of tickets work just as well as the old fashion
tear off tickets but you won't get that ticket stub as a memento. I
find them much more convenient than Will Call.