Rear Door Locking solenoid - Replacement

My Octavia SE Estate (2013 plate) has contacted a weird noise! when I unlock the car, I get a weird 'squeak' from the rear Drivers side door! I think it's the solenoid for the central Locking!

I've a couple of questions.

1, do you think it's the Solenoid? or could it be something more sinister!?

2, How easy is it to replace the Solinoid? (I'm sort of handy with a Trim removal tool and Socket set!)

3, Does it need 'Coding to the Car' ?

4, How much is it likely to cost me? I've had a look on Ebay, and there's a minefield of switches on there!

I've really like to avoid going to the garage for this! as I just can't afford the Labour cost!

Cheers in advance!