Got a leak coming from gear selector

I have a 727 trans and i have a bad leak coming from my gear shifter selector is the a seal or grommet there that could be bad. If so can i get this part from the parts store or will i have to go to a transmission shop. I looked under car and i could move gear selector up and down and fluid runs out. Also when i take it out of park it just falls right into drive and i cant tell which gear im in unless i take foot off break it doesnt click or anything. Sometimes when i put it in park and turn it off somehow it slips out and i cant start car unless i pull up on lever. Can someone please tell me how i can fix this problem. Thanks alot