Here in China, I hear everybody say 要考驾照 yao4 kao3 jia4zhao4 (if you search the expression on Google, you'll have 1,400,000+ matches).
(Never heard 参加驾校考试, though it's grammatically correct and understandable - only 96,000 matches on Google).
驾照 is the abbreviation of 驾驶执照 (driving licence)
错别字 is a noun (means "wrong characters"), you cannot use it as a verb.
You could say 如果我写错别字, but it's very specific (if I write wrong characters), you can simply say 如果我写错了 (if I wrote (it) wrong)
Hope it helps!
Pascal