Ok let me see if I can explain you and i will try to, because I am sure some dealers will charge people a lot of money for absolutely no work done at all
if you need to access the timing chain.. well you need to remove the engine from the car, that's the 1st thing, 2nd once the engine out you have to remove all accessories in the front of the engine, the injection system on top of the engine the rocker cover ( not sure if we say like that) water pump etc etc ..
I will try to explain in pictures, I was in Maserati dealer and I saw an engine outside in a bench from a Ghibli being dismantled by a mechanic and an expert was there to take pictures, as the car was sold as second hand to a client and almost a year later the engine seized solid, so they all try to figure out what happen what made that happen, was the client who did something or was a default in the engine etc unfortunately I did not take my self pictures, as the expert would not allow me anyway.
this is the engine V6 either 430 or 410 ps it is the same basically the same
in red shows where are the timing chain basically inside the engine
to access that timing chain ( there is one in each side ) you need to remove the front of the engine completely .. picture below , the timing chains are hidden behind all these front engine pan ( that is just the lower part, is missing the upper part of both sides on the picture)
where you see these pan on the engine but a lot of accessories and parts have been already removed
and here below the engine when coming out of the car, more complete to show the massif work that needs to be done
basically all front-engine must come off with all the pullies belts accessories, fuel injection system header, water pump, rocker covers Oil pan, oil filter etc etc till it looks like this
if you have to do this.. jisus prepare your wallet
Some confusion comes from the name Ghibli V6 biturbo, actually, it is the old model 2003 for example that had a timing belt. meaning with covers to give easy access without dismantling the engine apart and was part of the regular maintenance service