no itll be the starter motor, i just did mine yesterday, mind you put 2 hrs aside for the job, its a bit of a job moving everything to get at that top 18mm bolt.
once its off use mole grips to get the 2 7mm bolts started, wish i had cos the spanner just rounded them straight away. its pretty easy to fix, i just put a dab of grease on then wound it, didnt need to wipe it all down as its just grease