Don't fret

I cleaned a roset suite yesterday, funnily enough! From the picture, I'm not familiar with that fabric on a roset - does it have a pile or is it more of a flat weave kind of fabric?
Roset suites are quite expensive and despite their size take a decent amount of time to clean. Don't be shy charging a decent amount for it, the customer should perceive plenty of value in the price.
It looks a bit grubby, or is it just the photo making it look like that?
You can do a test clean on these, just turn it upside down, the fabric goes underneath. Remember though that it'll need propping up to dry, don't put it back on a carpet or floor when wet.
I'd be shocked if you couldn't give this a damn good seeing to with HWE.
My approach would be first to give it a nice long dwell with M-power, wetting the milk spills generously. Then, I'd apply heavy duty microsplitter all over and agitate it very very well. Extract with acid rinse and dry with fans.
Those are the products I use, others will obviously do the same job, I'm sure the next 3 people to reply will recommend what they use themselves

Have fun with the folds, it's like a sharpei dog - there's twice as much fabric there as you think! Go horizontally and dry in the folds with a towel so it's not too wet. Careful with the buttons.