You can also do the headlights with a heat gun - you have more control that way with temperature and whatnot, though the job is long enough going to the oven route, this makes it more time consuming, but overall probably less disturbing for the wife

I think bernardi parts here on the forums sells them at a decent percentage less then what you'd be paying directly from a regular honda dealership. Just order them in NHBP.
But, honestly the headlight project is fun, yet challenging, but the results are very satisfying especially if you like that feeling of accomplishment. Expect to have the headlights off the car for a solid day though, to do everything right. Forum member smeister has an excellent how-to about the entire process.
As far as inexpensive mods for the fit, an aftermarket shift knob can do alot fo the interior - I got mine on ebay for 10 plus shipping, and I'm very pleased - it was a no name brand, but it's threaded specifically for hondas, so no cheap screws that tighten to fit around the shift level, like the ones typically sold at autozone, pep boys, etc. Just search for honda shift knob and make sure the description indicates it's for Honda/Acura only, or email the seller to confirm.
Another cheap cool mod are blue LEDs (or the color of your choice) for the floor, below the dash and glovebox. You can find an easy DIY here
http://www.fitfreak.net/forums/fit-l...ome-light.html
Whenever you unlock the car (with keyless entry) remove the key from the ignition, or do anything that will cause the dome to light, so will these. It looks awesome, IMO, I have them in blue, to be similar to the OEM JDM blue footlights. You can get these as 9" or similar LED strips from autozone, etc. for about 9.99-12.99, and get some extra thin gauge wire to run the extension from the passenger's side to the fuse box. It's easy and the results do wonders for the interior. Also, changing out the dome and trunk lights to LED panels is also nice - I picked up 9 LED panel units from pepboys for 21.99 each and they come with adapters that will literally plug into most common bulb sizes for interiors like 194, 168, etc. Another cheap nice looking trick. All you need is a flathead to take off the clear plastic to access the lights, another 5 minute project.
If you want to go with some performance, there are alot of decent axle-back systems for reasonable prices, namely those from megan racing and a-spec products. A-spec is a fitfreak vendor, and invisionfit.com sells the megan one, among others, for a great price. You can probably also see if they'll give a fitfreak price break, their forum user name is InvisionFit.
And another thing that is relatively cheap and moderately easy is changing the badges for the red OEM Type-R style ones. There's tons of How-to info about this on the forums, just go into the thread about JDM Bodystyling.
Oh, and another thing is painting the wheels. While it sounds tacky it can do wonders for the styling of the car. The OEM rims on the sport model are great, and if you have a base fit, they're a reasonably priced upgrade from the 14" steelies, alot of forum members sell their OEM sport wheels on here since they go the aftermarket route, but I think it's fun to work with what you got sometimes.
Duplicolor makes a whole system for painting wheels - primer, color, clear/sealer. Have heard good things. Mine are flat black and from far they look aftermarket.
It all depends on how much work you want to put into it - for me, the fit has been a big learning experience, as it's the first import I've had a chance to work on, all my previous cars were domestics, and all except my 84 corvette were POS. Which is why I only have the 'vette and the fit

Get creative, I got alot of my ideas from the forum and used them as stepping stones to doing things in my own little way.
have fun with the fit first and foremost, that's the type of car it is, it just evokes fun.
and and so my post is not completely off topic - magical hp computer chips magically put your car in the repair shop and probably also cause things to vanish - like the warranty.