Yeah, spray the gasket and pan with brake cleaner. I usually have good luck re-using the old gaskets without leaks as long as everything is clean and dry.
The valve body is pretty straightforward to replace. Gotta remove the shifter lever that slides a piston in the valve body, a few 10mm bolts and one connector iirc. Make sure the fluid level is perfect though, you have to have them good and hot. There's a fluid temp/fluid level chart posted somewhere on the forum.
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View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)