Speedo drive is reasonably easy once you see what needs doing.
The lugs MUST be in the correct holes, if they aren't you will do the wheel nut up, then they will simply snap off and you obviously won't have a working speedo.
Always worth a good dollop of grease when refitting it as well.
A new chain can cause road noise as well, or even if the wheel has been slightly adjusted and offset, the chain cuts a new path on the chain guide causing a burring noise.
It's especially noticeable if you upgrade your chain to a heavier duty one.
Have a good look under the sprocket cover and make sure there is nothing untoward going on, and also to see what sprocket nut is on there (if there is one
)
The new modified nut will look totally flush with no spare threads in view at all.