transmission seal HELP!

[mlswoosh]

my tranny's been leaking abit (right under the shifter, where the the tranny connects to driveshaft), smells pretty damn bad... my mechanic told me all i need is a brand new seal, i just want to make sure if this is what i need... a "extension housing seal"?

http://www.trademotion.com/partlocator/index.cfm?action=getLocator&siteid=722&chapter=APF613&appSectionid=13&groupid=60534&make=25&model=240sx&year=1998&catalogid=1

thanks,
Mike