Yep, something like that.
Basically there are (ie. German, just to give HoHun the creeps with my 'kitchen-german'
: Rüstung = 'equipment', zustand = 'state/quality of stg' , satz = ~'material'; bau = building, producing -> umbau = 'conversion')
Rüstsatz : field kits, available for all planes, like droptanks, bombs, gondolas. Noted with Roman numbers (Rüstsatz IV - gondolas, for 109K), does not change the plane designation!
Rüstzustand : something like additional equipment from the factory. Recce camares (ie. G-6/R2), piping for underwing droptanks on LR reccess, autopilot etc. It is noted in the designation, ie. K-4/R6 was to be a bad weather fighter version with autopilot, not one with gondolas!
Umbausatz and Umrüstsatz : No idea between the exact difference between the two, perhaps butch can tell, but these are more like serious conversions rather than adding just something extra, also factory done. Things like GM-1 (G-6/U2) or MK 108 fitting (G-6/U4).
Trouble is, that sometimes the same thing has two designations, or the designations changed, or disappered when something became standard fitting.