If it was cheap low grade oil then it'd be a good idea to change it anyway. Putting some Redline shockproof lightweight oil in would be a good idea, it makes shifts feel super smooth in my opinion.
I think your clutch would be fine if it's not slipping under high load.
Does the car want to creep forward with the clutch disengaged and in gear? And also does the clutch engage quickly when you just lift your foot off the floor rather than your foot coming off the floor a bit and then starting to engage? It's what is usually called the bite point, the point at which the clutch starts to engage when you lift your foot. You can adjust the clutch pedal to have the bite point close to the floor or you can adjust it back so you have to lift your foot further off the clutch pedal to engage it.
We need to know where the bite point is to help clarify the problem a bit more.
T