argh, did you fill it thru the plastic bung on the top close to the engine block? if so you might have fked your clutch. that is NOT where you fill the oil, that is the flywheel inspection hole so you can set/check the timing

the correct place to fill the oil is the 17mm allen plug on the side of the gearbox, you fill it till oil starts to comes out of there. though what I would do is take out the filler/level plug and fill it thru the speedo cable/sensor hole near the back in the toip, much easier.