Hi,
Where's it leaking, exactly? Do you mean the front seal is leaking?
There's a ton - probably more, actually - of info on the site (and growing daily) about the rear diff. The search engine is great. Have a good read around and see if you can identify what the issue is.
I'm putting a rear axle back in my car at present. Read that post, and the ones by: Jeffc280, George Des and Waqas (search engine lets you search by member).
Finally, you don't need special tools to do any of these jobs, but you do need a good array of normal tools.
You probably don't want to be splitting the diff if you haven't gone through it before with someone who knows what they're doing. And you can't do it without taking the axle out of the car first.
JH