As I mentioned earlier, I haven't seen the ELH. I was going off my knowledge of the 2e big-arse-magic rules, which Psion confirmed are rather similar. Thanks to Blacksad for confirming stuff like that is still possible.
As to what level you'll need to do something like that, I'm guessing quite a bit. Remember, though, that items that boost skills are pretty cheap compared to other items.
Again, I haven't seen the ELH, but for a 30th level character, it shouldn't be too hard to create a +30 or +40 to spellcraft item for just this sort of thing. If you're 30th level, you could have up to 33 ranks in spellcraft. Figure a modest INT bonus of +5. Maybe even Skill Focus. That gives us +30 +33 +5 +2 = +70, before you roll any dice. On the average, you're looking at +80.
I'm guessing you could still do some icky stuff with a DC 80 epic spell. And that's not even "hardcore" min/maxed. No Archmage or Loremaster or anything like that.
Can anybody with a book give us a DC 80 as a sample.