87 Turbo coupe transmission

[Big-H427]

I have an automatic 87 tbird turbo, the trans is leaking very bad near the converter pump shaft ?. I was going to install a new pump/shaft seal (which looks fine) but the seal looks like its pressed in then it looks like someone took a chisel and set it in place by notching the case over the seal in several places. Is this normal, can I replace the seal at home or is this a trans shop only fix. thank you