Magnifica S 320.B repair

Hello,
I've had a magnifica S 320.B for 8 years, it's always worked very well, I descale and change the filters regularly.
But now I notice that the coffee comes out colder than before, despite the temperature being set to maximum, and above all the quantities have just dropped sharply.
I used to make a cup with 2 long coffees, but for the past few days I've needed almost three.
I see on the net that you can find all the repair parts, but before I get started I'd like to know what to change and in what order.
I've noted that the grinder, infuser, pump and card would be items to change on a machine of this age, but before changing everything, maybe there's one main item I should start with.
Thank you for your advice.