Spellfire ---> Frozen Shadoweave..?Follow

Hi all, my question is one that has prbably been asked before, so sorry if this annoys anyone! Basically I hit 375 with my tailoring and as I was fire spec I created the spellfire set for my mage. Now i'd like to spec frost though so i'm thinking the best thing to do is creat the Frozen Shadoweave set.
My question is this though: Obviously i'm gonna have to drop spellfire tailoring (cant remember what itas called) in order to take up Shadoweave. When I do that will my tailoring skill go back down to 350 or will it stay at 375?
Thanks in advance for any help on this matter. Also do you think i'm doing the right thing by changing? I mostly do 5 mans and heroics and a little PvP.

Thanks again :)

Not exactly sure why you are switching to frost (assuming for raiding) but all you do is pay I believe about 150g and you can learn the other one, your skill does not go down, it stays at 375. But as stated, I wouldn't spend the time crafting the gear, the set bonus blows for mages, just work on getting badges for gear.