84' Yota - 4x4 front diff. leak

I've had a "slow" leak on the front seal at the drive shaft for a while now it's become apparent that I need to fix it as it has become a big leak and is spraying the underside of the truck.

How difficult is it to pull the shaft and replace the seal(s), by the looks of things the front diff has "never" been worked on. Is this something that a novice can do or is this a Mech. shop  process ? If novice what tools do I need ?  

The only hard part in replacing the pinion seal is retorquing the nut to get the proper pinion bearing pre-load value.

One way to ball-park it is to use a torque wrench to remove the nut, slowly increasing the setting until you break the nut loose, then retorque to that setting.

You can find and download an FSM online, and follow the steps in the manual.  
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seen in FOUR WHEELER magazine July 2006 and OFF-ROAD magazine Feb 2007

'84 4Runner SR5 -
ARBed 5.29s F&R, 4.7 & 2.28 t-cases, 2" drive train lift, AP hy-steer, BudBuilt x-member/skidplate, 36" TSLs, 30 spl Longs, Chevys, rears up front, winch, yada yada ...

'80 something Toy P/U -
Buick 231 V6, Holley 4 bbl, Weiand intake, Downey headers, TH350 L/U w/700R4 low gearset, dual tanks & batterys ...

89 4Runner SR5 -

Like Fourwd1 said, it's a pretty straight forward operation if you're mechanically inclined. If you're not its a cheap job for a shop to do too.  
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Long Travel 4WD - The best of Both Worlds

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Guys - Thanks for the input. sounds like a job for my mech. to do.

p.s. would this leak keep my front diff from unlocking the front hubs ? for some reason in standard 2 wheel my front dif is making a whirring sound then a clunk when I come to a stop, when I put it into 4wheel high the "whirring" does not happen.  Any comments would be helpful.

Pacaguy0