my opinion is a little different. i'm 56.
i was diagnosed at 46 and really only started to need meds about 3 years ago. the progression has been pretty rapid in the last year and i depend on sinemet to lead a halfway normal life. i've tried every supplement you can imagine and they have had little to no affect. you need to ask those who are recommending alternative therapies to list everything they are taking, conventional and alternative. i shied away from conventional meds far too long, hoping my vitamins//amino acids/supplements would magically alleviate my symptoms and as a result put up with a lower quality of life than i needed to.

the best thing in my opinion for your father is vigorous exercise, staying healthy and finding the best movement disorder neuro he can find and have an open mind about conventional drugs, at 68 in my opinion you want your father to be as active as possible and have the highest quality of life, not having limited mobility and energy because you think meds are bad . if you decide to go with a naturepath, get proof that their recommended treatments improve one's quality of life and if they claim their supps slow progression, ask for the proof. you may just spend a fortune on tests, treatments, more tests with a naturpath. remember, sinemet has levodopa, the precursor to the natural neurotransmitter dopamine, imho that's pretty natural.
i tried IV glutathione, chelation, etc. and just wasted money.

in terms of meds, i found the dopamine agonists intolerable, they caused drowsiness, swollen feet, brain fog and i tried too long before giving up and switching to sinemet. the point is, everyone is different and your father needs to find a neuro that will work with him to provide the drug regime that will give him the best quality of life, assuming he even needs meds. that regime might take a few months of tweaking meds, dosages and even brands if you are taking generics. working out a diet / eating schedule is just as important as meds since protein can interfere with sinemet. if i eat any protein an hr before my meds they have almost no affect.
azilect is a new drug that might offer relief and be possibly neuroprotective. there are newer extended relief drugs and patches that may be back on the market. a neuro that just sees a few parkinson's patients may not be the best choice.

there isn't a magic alternative bullet yet. just my opinion. but there seems to be more research on non-drug treatments that attempt to insert cells or genes directly into the brain than ever before.

not sure why you think vitamin c would benefit, there have been studies showing vit. C and E don't slow progression. even the coq10 study in my opinion was borderline positive.

just my opinion but it's amazing how 1 study, usually in mice or rats or years ago gets cited a thousand times over by supplement manufacturers.

You have noticed by now that we are an ornery, opinionated bunch of so-and-so's. That's part of why we're still going. A lot of us are pushing the 20-year mark and not only still on our feet, we're still throwing punches. It makes NT a different kind of place.

There are two things that are pretty well proven to stop or even reverse neurodegeneration. Unfortunately, they are radical and difficult.

One is exercise, my own weak spot. Beat me with a stick and I might do a little, but not near enough.

The other is caloric restriction. Not eating less, rather eating less often. Take your vitamins and eat every other day, as much as you want. On the fasting days your body gets a chance to clean house. Our ancestors would kill a mastodon and eat it. They really weren't hungry the next day. "Aw, Maw! Not big, furry elephant again!"

From a Darwinian viewpoint, what puzzles me is how my pudgy little ancestors were able to catch or escape a mastodon.

http://www.michaeljfox.org/research_PPMI.cfm

Again I can't than you all enough for the replies. i read each and every one of them to my father and researched everything you recommended.

I'm still doing ALOT of research, but at this point it looks like Curcumin and CoQ10 hold the most promise (I'm still looking into a BUNCH of other stuff.....resveratrol, transdermal magnesium, etc....). For those of you thinking of curcuming, you may want to Google curcugel. It seems to be the best curcumin as far as bioavailability.