Dear Sir or Madam:
The answer to your question really depends on what you mean by the term "engineer." If you mean it in a way synonymous with "wireless networking professional" then you probably don't need to worry about pursuing bachelor's and master's degrees in electrical engineering that will allow you to take the Professional Engineer (PE) exam and then call yourself a "wireless networking engineer." OTOH, if I'm wrong about this, you'll want to start looking into engineering schools that offer radio/networking degree programs, such as Perdue, Cal Polytechnic, CMU, and so forth.
If your real goals are somewhat more modest, you have any of a number of possible points of attack, investigating any or all of which will also inform you about the amount of training involved and the kinds of skill sets you would want to develop:
1. AAS in Wireless Communications: lots of technical schools and community colleges offer this kind of degree, and/or related certificate programs, so these are definitely worth looking into.
2. Planet 3 Wireless/CWNP program: check out the various certifications offered at www.cwnp.com; you'll find the CWTS and CWNA particularly good places to start.
3. Cisco offers wireless credentials that tack onto the CCNA, and in the CCNP and technical specialist tracks. These are also well worth looking into.
HTH, and thanks for asking,