If its a wet clutch, I would be surprised if it needed a basket replacement, particularly that it is a 620 and doesnt have a lot of HP going through it!
A clutch pack would be all you "SHOULD" need and I'd probably throw a set of springs at it!
It really is only a matter of removing the clutch coverm undoing the spring retaining bolts (Evenly all around, not one at a time) so the pressure plate comes off evenly!
Take the plates out and check overall pack height (Thickness) with the new one just to make sure all is the same or very similar, and then replace the old with the new!!
I would think their would be a small bearing in the pressure plate, and it would be a good idea to replace that!! (Cheap at a bearing service)
Before sealing the cover back on just replace it dry and make sure the system releases/operates ok ! If all good seal the cover back on and away ya go!!
Take your time, be methodical and as you remove things lay them out in the order you took them off!
Oh by the way, dont overtighten the clutch spring bolts, they can snap easily! Give them a nip up (not sure what the torque setting would be but 15-20nm would be close!? Anybody??)
The springs will push against the spring retainers and hold the bolts as well!!.
Hope all this helps!!