Well, maybe you cannot learn to be a professional wedding photographer in 5 months, but if you have the time and the drive to do it, taking a photography class at a community college or adult education program may help. Alternately get a book or two and learn about picture composition.
Before digital, when you had to pay for each and every picture to be developed (and printed) you made sure twice that what you had in your viewfinder was what you wanted to pay for... now it's just a matter of keeping your finger on the trigger and hoping that one picture has all the body parts and is in focus... still it really helps to learn about proper composition, exposure and lighting.
Do NOT go out and buy a ridiculously expensive professional camera. Get a mid-rage digital SLR if you don't have one yet. Get a camera that you can learn how to use. A camera that requires ridiculous software to get decent pictures out of it is NOT worth it. A camera that has so many "extras" that you cannot work the basics is not worth it. Get a good versatile lens with it. If the wedding/reception is inside consider getting an external flash.
Many professionals and even ambitious amateurs spend years deciding on which equipment they like, which brands they prefer etc. - they accumulate most of their stuff slowly after testing it out - even if you were to decide to go professional - don't drop a bunch of money on it for this occasion.
Before the wedding take LOTS of pictures. Work your camera, get to know it, look at the pictures you have taken, evaluate their composition and lighting, play around with the camera's settings. 5 Months is a lot of time to get comfortable with it. Learn how to use a photo editor (but upgrade if you decide to stick with elements).
When the day comes take LOTS of pictures. Keep your finger on the trigger, have extra memory cards. The more pictures you take the greater the chance that there will be some nice ones.
I used to be REALLY into photography (digital kind of killed it for me...) an ambitious amateur you may say. You can take very nice wedding pictures as a hobbyist with hobbyist equipment, but they will be more the "action shot" kind of pictures. Portraits and staged shots just don't come out as nice without the proper equipment and know how. As long as your friend knows that, it should be ok. Maybe they can have a few staged shots taken by a professional and you do the actual wedding/reception. That should come out cheaper than hiring a pro to do the entire thing.
One more thing: hiring a "pro" unfortunately is not guarantee for good pictures. I just received photos from a wedding we attended and the couple paid for a professional photographer and videographer, at least a few thousand $$$. A lot of the staged photos came out like c$%p. Out of focus, shadows on the bride's face, overexposed, underexposed just blech. Sure within the 5000 pictures (they sent us a DVD) there were a few nice ones... particularly of the ceremony and reception but I kept thinking that the staged ones (that they spend 5 hours! on taking before the ceremony) looked like they were done by a beginner... they had all the fancy equipment, but apparently none of them (there were 3 of them) had ever taken a class in proper picture composition and lighting.
Good luck!