Matt
Don't be scared, do your tests first, if everythings ok just get on and clean it. Can't see what all this mystery is about cleaning upholstery, worst part is the strain it puts on your back.
I try to avoid using too many products on upholstery. Find out what the material is and use a suitable product for that material, occasionally you may need to use an additional product for some stubborn areas such as hair grease marks.
It is good to have a system which can make the job easier.
Personally I take all the cushions off, after doing tests. Then I clean the frame of an armchair, if thats ok I go on to clean the frame of a sofa. Then I clean the cushions, pyramiding them on the sofa whilst I clean the last chair (3 pce) with an airmover blowing on them if required. Cleaned hundreds in 11 years and never had a problem.
I'll probably knack one next week now!