Re; Tutors and cantrips

[median]

For reference some of the work for this has been started here,
http://www.themanadrain.com/index.php?topic=41627.msg577725;boardseen#new
I have a panglacial wurm that I want to cast from my library, can I use chromatic sphere to aid in the casting cost and draw a card?
If so, when do I draw the card? If I can draw the card, do I have to shuffle first?
If I don't have to shuffle, can I cast a brainstorm or use a sensei's top while searching my library if it's to my advantage?
Lastly, can I use a top or brainstorm after casting lim-dul's vault (during the process of rearranging my library with lim-dul's vault.)

[luma]

You can use Chromatic Sphere. You draw the card as the ability resolves, which means that you're still searching your library. Note that even though you're searching, you can't change the order of the cards, so the top card (which you'll draw) is still the same card as before you started searching.

You can't cast spells or activate abilities while resolving another ability, so you can't use Top or cast Brainstom either while searching your library or resolving Lim-Dul's Vault. Panglacial Wurm and some other cards give you a specific permission to cast the card while a spell or an ability is resolving.

[Filth]

the top card (which you'll draw) is still the same card as before you started searching.

...unless that card was the Panglacial Wurm. When you cast the Wurm from your library, you first move it from your library to the stack, then get a chance to activate mana abilities (such as the Sphere's ability) before paying the Wurm's mana cost. So if the Wurm was on top, it has moved out of the library before you draw the card from Sphere, and you'll draw the card that was under the Wurm.