Shoulder Arthroscopy

I have been advised that after a recent mri scan (on my  right shoulder) which didn't show anything of any significance i now need to have keyhole surgery for further investigation. I have a few questions to kinda put my mind at rest i suppose!
If the scan didn't show anything of any significance does that mean that there isn't actually anything wrong with my shoulder? - the surgeon originally thought i had a ruptured bicep tendon.
If there isn't anything wrong with my shoulder why do i experience such pain especially at night?
How painfull is the keyhole surgery?
How long do i require off work? - i have a physical job involving lift.
If anybody can answer any of my questions  i would really really appreciate it
Thanks

[Dr Vinod]

Arthroscopy can also be performed just for diagnosing and checking . Arthroscope, a type of endoscope that is inserted into the joint through a small incision may be max 4mm. A special fluid is used to visualize the joint parts.

Ask your Physician/Surgeon the significance of an Arthroscopy for only diagnosis of your biceps problem as you already have an MRI report.

Does he want to go for keyhole surgery or something? Let him explain all pros and cons and this would not be very painful, but only go ahead after you are clear with everything.

Take care!