You just need to make sure you can remove the filler plug first before you remove the drain plug and remove the oil, once the oil is out you cannot drive to a garage and ask them to help you get the filler plug out as i found out to my cost.

Hi, I have the same problem, new clutch fitted by the garage before i got the car, i knew the gears where stiff when i got it 6 months ago so i changed the oil and added moly slip but still the same, great car to drive and loving it but i wish the gears where not so stiff, no idea what to do...