Let's imagine I wanted to replace the words "the sash" in this sentence with "Worf's silver sash." Can I say wo'rIv SIrlIy Ha'quj as the subject, or does that not work, since SirlIy, being a noun, cannot be used as an adjective in the same way that, say, SuD can (unless SIrlIy can also be a verb of quality meaning 'to be silver-colored' as well)? Or, would I need to express the subject of the sentence as wo'rIv SIrlIybogh Ha'quj, or (more likely) wo'rIv SIrlIy yughbogh Ha'quj ('Worf's sash which is made out of silver') instead?
I realize there may also be a difference here in whether the sash is simply a silver color, or actually made of elemental silver. But I assume you'll tell us if that's the case. :)
Can I say wo'rIv SIrlIy Ha'quj as the subject
You can. "The sash of silver of Worf."
or does that not work, since SirlIy, being a noun, cannot be used as an adjective in the same way that, say, SuD can
You are correct that SIrlIy is not used in the same way as SuD. SIrlIy is a noun and SuD is a verb. They can each be used to modify a noun, but the mechanism is different. To modify a noun with another noun, you place the modifier before the main noun: SIrlIy Ha'quj ("sash of silver" or "silver sash"). To modify a noun with a verb of quality, you place the verb after the main noun: Ha'quj SuD ("yellow sash").
would I need to express the subject of the sentence as wo'rIv SIrlIybogh Ha'quj
No. SIrlIy cannot be used as a verb.
or (more likely) wo'rIv SIrlIy yughbogh Ha'quj
That is a possability. You could add a -'e' to the Ha'quj to clarify that you don't mean, "Worf's silver which the sash is made out of". I would also suggest moving wo'rIv: SIrlIy yughbogh wo'rIv Ha'quj'e' to make it clearer that it is the sash that is Worf's and not the silver that is Worf's.
In the end, I think your first suggestion was the best of those options, though, again, I might move wo'rIv for: SIrlIy wo'rIv Ha'quj "the sash of Worf of silver". But that's purely a style decision and your style may differ. Heck, tomorrow my style may differ.