One quick question, can I still accept the lurkers aid on a spell even AFTER rolling the dice and failing the skill check? I'd say this is "thematicaly" possible, but unsure as if the rules allow it, seeing as you can decide to use clue tokens after a skill check is rolled knowing the result of the roll first.
No. When you cast a spell, you exhaust it whether it fails or passes. So if you fail, you cannot then try to cast the same spell as it is now exhausted and unavailable to you until you refresh it.
If you have a free hand and if you have a 2nd copy of the spell, then you could use the Lurker for this 2nd spell.