Bravo3 gear oil leak repair

[Hardrock]

Hello all,
New here. I have a bravo3 leaking gear oil back into the boat where the shaft runs through the transom. Water does not get into the drive.

My question is, how many different seals are there in the top of the drive that could let this happen?

Also, are there any special tools need to replace these seals?

I've been getting different opinions from people with different labor charges as to how long or what the cost will be to fix it.

I've swapped outdrives on other boats and it didn't take but a few minutes, now I don't have a stand or a hoist so I haven't removed ths one.

Also, isn't the upper end of all bravo drives the same?