"noun or participle with aux. verb する"

Hi there,
I´m studying japanese and if I look in an online dictonary some things differ from what is in my book.
For example for しょうかいする the dictonary and my textbook say that it´s a class 3 verb with する.I get that ...and I don´t need/am not allowed to put a -を- in between...right ?(First Question)
SO... on tangorin.com (the dictonary) there it is written that you would write しごとする, whereas in my textbook there is written that it had to be しごと - を - する. I know that the を version definately is right... and I´ve never seen/heard "しごとする"... but there are a like a few dozen words I wrote on cue cards where now I don´t know if I have to write them with or without -を-... I will have to check in my book and just do it the way the book states it... But I want to know if it´s even wrong to write "しごとする" or if generally... or.. in specific situations it is used that way...(Second Question) maybe I just misunderstand the dictonary.. but the description for しょうかい and しごと both are the same like "noun / noun or participle with aux. verb する".. Please Help !

Those verbs are called -suru verbs. Almost all stems of -suru verbs work also as a noun, so ～する and ～をする are both valid in almost all cases. It's not so common to insert を for some -suru verbs (e.g. 到着する, 下降する), but をする is natural when the noun is modified even for these nouns (e.g. 予定外の到着をする, 急激な下降をする). You can check whether the noun is also a -suru verb or not in decent dictionaries, as in the explanation in your dictionary "noun / noun or participle with aux. verb する" . Of course, there are some exceptions, as I wrote "in almost all cases". For instance, 熱する is a -suru verb, and 熱 is a noun, but 熱をする is invalid even when 熱 is modified. Similarly, 恋する, 愛する and 恋をする are all valid, but 愛をする is invalid. These exceptions are not so many, though.


Explanations in other dictionaries;
しょうかい【紹介】の意味 - goo国語辞書
［名］ means 名詞, i.e., "noun", and (スル) is スル動詞 "-suru verb", so these definitions show that 紹介する and 紹介をする are both valid. It's "Noun" and "Suru verb" in Jisho.org.
仕事 - Jisho.org