not a major job.washing machine is easier because its not hidden,and you dont have to take off the plinth that fills in the gap between floor and underside of units.
the standalone jobs offer more choice and are generally cheaper but wont it look odd being different from the units either side
all the supplies you need are already there ; water in, waste out and electrical point
just check the width between units to make sure the replacement will fit
ps has to connect or prop to underside of worktop. (all 4 feet are now adjustable when in final position with modern appliances,) because of overbalancing. u know weight of drawer/trays when full and pulled out for loading/unloading