hi,
if it is a timing belt then there should be no oil there (i believe), so it looks like a seal is gone, which would probably mean taking out the front puley and crank sprocket etc before getting to the seal. the timing would then have to be carefully redone.
if it is a timing chain, and the oil is coming from the crank pulley area, then you could probably do it and not disturb the timing at all. (the front pulley with ancillary belts would come off and the oil seal would be accessible then) you dont need to take off the crank sprocket.
cheers