It's mainly the weight of the bloody thing i.e it takes two people to lift one.
After that its all the bolts thaty need removing to get it out, if one or two of the little sods start playing up it all adds up.
Then its getting the correct parts to put it back together if some of them are wrong, then its a couple of days to try and get the correct ones from renault.
I would take it to some one who knows the cars inside out. Dave sibly, Stu Harding, Andy Rabson, Craig Righton, Lee Alison, and some time's me.
Dave, stu and Lee are all experts at changing engines and gearboxs. Lee having the advantage of a 2 post lift and gear box jack.
Stu having the advantage of being a renault mechanic and rebuilder of gear boxs.
Dave, just because if you cut him in half he says "renault 21 turbo" like a stick of rock.( also he is a mine of usless info on these cars).
I hope that helps.