You may have the heater vent door(inside the dash) open all the time and the heat from the heater core is dumping out behind the CCU and radio as well as the gaping holes. I'd check to see if they replaced the carrier bearing also and not just the flex disc.

As to repairs, how long and wide are the cuts in the tunnel? if not too long or wide then there is a metal epoxy available at the auto parts store in a tube. called Miracle Putty or some such name. It is a two part epoxy putty you kneed and use as much or little as you need. it hardens like metal and you can use a spatula thingy to apply to the cracks. Can be sanded and painted also
Good stuff.

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1986 Euro 500SEC "RUF" 9:1CR, "Rose"
1985 Euro 500SEC Cabriolet AMG Widebody
1982 Euro 500SEL "Blue"
2001 Texas Heeler (Aussie/Queensland X) "Sulphie",
2012 Queensland Red Heeler "Squeak"
Best dogs I've ever had.