leaking trim fluid

I have a 1995 171 with 115 Merc that is leaking trim fluid out of the top where the shaft goes in and out. Its a slow leak and have to add fluid every couple times out.

Anyone know what I need to buy to fix this?

Is this somthing I can take care of on my own or do I need a mechanic to do it.

Thanks,

Jon

Might get better results if you post in the mercury forum. However it is a seal replacement that requires disassembling the cylinder and replacing the seal,