Thats probably the rear main bearing oil seal which was a problem on early Ecotec motors...it will just leak oil and probably slowly get worse. The only power you may lose is if the oil leaks so bad that it gets on the flywheel and then onto the clutch plate which will cause the clutch to slip. If its just weeping I wouldn't worry but if its dripping continuously then I'd get it fixed.
well that said its $150 to fix so cant be anything really bad but it has been leaking for awhile now never bothered to get it done, is crankseal part of the gearbox coz sometimes it makes abit of a noise when changin gears.
nope it's the very edge of the engine before the gearbox. noiosy gear changes could be as simple as needing a lil more trans fluid, or it could be synchro's dying
The gearbox takes Dexron 11D trans oil and there will be a filler plug on the drivers side towards the rear of the gearbox - it has a recessed hex head for an allen key. You originally said the 'crankseal' was leaking - crank means crankshaft which means the engine?. If they want only $150 to fix it then it must be simple as $150 wont buy much.