front seal

hey guys so i had a guy come out 2 see what the problem was and he said that it was the front seal between the transmission and engine. he said that its gone and thats y it wont move at all and he said that a repair would cost about $500 just 4 the seal and in most cases if its not that than it would be the transmission and that would cost up 2 another $1000. if u guys have a better way of knowing how 2 fix this please let me know. i would buy the tools my self if its cheaper and work on it my self tell me what u guys thing about it. and if u guys could give me a price of how much this all would cost if this isnt right.