Is it possible to install a second pickup into a one-pickup guitar?

Yes, it's possible, but it's really a job for a professional luthier. A good luthier will measure the guitar to determine the correct placement for the pickup. Next, he/she will route the hole, drill a channel to the wires can be connected to a pickup selecter, The other pickup will also have to be connected to the pickup selector. Finally, he/she will install the pickup, the pickup selector and solder all the wires.

A pickup selector on a guitar with 2 pickups usually has 3 positions: neck pickup, bridge pickup, and both pickups together.

How much would it cost? Some luthiers charge by the hour and some will give you estimate for the etire job. It takes 2-3 hours to add a new pickup to a guitar.

But before your friend adds another pickup, he/she should consider swapping out the current pickup for a new one. The Dimarzio PAF is a great pickup for playing leads. There are other good pickups, and for recommendations, you should post your question at the Guitar Forum at www.harmonýcentral.com It's where the serious amateurs and pros hang out.

If you friend chooses a pickup the same size and shape as the original, the hole on the guitar doesn't have to be altered.

But before your friend does that, take the guitar to a music store where there's a good selection of guitar pedals. I'm thinking about what you said.. a very flat tone when playing clean." A chorus pedal should solve this problem. There's a lot of chorus pedals to choose from. Two of the best are the Robery Mayer Voodoo Vibe and the chorus pedals made by TC Electronics. If your friend likes to tweak a lot, then the TC Electronis would be a good choice. Eric Johnson uses the TC Electronics, but I prefer the tone of the Voodoo Vibe. There's cheaper pedals which many guitarists like too.

Have your friend try out a bunch of different pedals at the music store so he/she can see if any of them solve the "flat tone" problem. If there is, your friend should not be shy about asking for a discount. If the store doesn't reduce the price by at at least 15%, then your friend should look on Ebay.

It's usually better to try a pedal or swaps the original pickup for a new one rather than modfying a guitar. Plus, it your friend ever decides to sell the guitar and get a different one, the pedal will still be good,

another sad answer but the sad answering poeple at least read the question before getting on their high horse lol. Take it down ya local shop and the guy there will advise on kit. Shouldnt cost too much if you not after the top of the range stuff. You can get hte pickup placed in the body of the guitar and the leads etc will come out of the back like in a standard electro acoustic. if its a good acoustic then is it worth messing with? You could just mic it up instead and feed the mic to an amp.