rear differential drain plug

[gschesel at comcast.net]

Subject Audi is my '91 100, with 199k miles.  My new neighborhood (non dealer) Audi mechanic was to drain and refill the fluids in the manual tranny and the rear differential with synthetics.  No problem with the tranny, but the drain plug on the diff would not budge, and at some earlier time was screwed in till it was flush with the housing.  So all he was willing to do was check the level and advise.  The level was OK.  I assume I will have to tackle this myself.
Would it be wise to drill a pilot hole in the plug and turn it out with an eazy-out?  Any metal shavings would hopefully be drained out along with the fluid when it drains.  My guess is that the amount of torque needed to get the plug to turn loose will mean drilling a rather large pilot hole and use of a rather large eazy-out.  Or, should I leave it alone, suction the fluid out and then refill to correct level?
Any suggestions?
thanks
gordy
'91 200 20v
'91 100 quattro