No harder than changing one in a clio.
Are you fitting a k4m to a r5 or does it already have one in and you want to take it out?
To fit the k4m the easiest way I have found is to use mounts off a 1.7 r5 or a diesel that bolt to the subframe, If using the clio gearbox the back mount needs to be fabricated and most have the bolt holes for the r5 mounts. Or use an r5 turbo box or similar and mounts won't be a problem. Would recommend fitting the engine steady from the lower front of a gt turbo or gtx r5 as well. The exhaust manifold fits just nicely over the top of the subframe if you turn the brace in the middle of the arb upside down but will need modification to the down pipe to clear the body.
Hope this helps.