Based on your current style, should not be hard at all nor take much time. What takes time is fine-tuning it per say i.e. putting a spit shine on that sucker! Basic entry of color codes, specify images if using gradients and swap a logo (maybe search here for 3 Part Fluid Header and that will allow logo on left/tree icon on right etc).
^ All this based on just viewing the Canary forum in your link I didn't bother viewing the other site since you didn't specify for which site this would be but not hard at all if you know stylevars and what to edit.
Referencing this may help you do it yourself:
https://vborg.vbsupport.ru/showthread.php?t=256370
Don't become frustrated OR think it's too much to process, it's not just takes time like anything... working on a car etc

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