That's a drag...It sounds like you did it right. Like you I bought just the (corteco) seal and re-used the alum housing. I focused on getting it level/even and tried to have its installed location somewhat different than the original location of the seal. Mine isn't leaking.

How soon after you started it up did it start leaking? The steady "drip" you mention has me wondering if it is something other than the rear main seal, which should be more of weep. Either way, you are probably going back in. Should be easier/quicker the second time.