Ooops, the bike in the pics in the link he posted has stem shifters, but in his original post he clearly states downtube shifters. My mistake.

Oh maybe your a candidate for the electronic shifters ...

I hear that being with a woman is a bit better. It's on my bucket list anyway! :)

Ok reality is it's an old Schwinn, and so brifters are not an option ,
though buying a New Bike, already built up with them Is.

Retrofitting a pair of bar ends may not be possible either ,
because the ID of the bars where they would go,
is too small , steel drop bars rather common in that era.

They are steel so its after the bronze age ..

I recommend: Shopping , Post Xmas , pre taking unsold shop inventory for the taxman, a good time.

I just found out today that my great uncle (who I have never met, but my parents know well) use to collect bikes & cars. He has 5 nice bikes, one of them being a $3500 carbon touring bike he said he can sell to me for around $250-300. So I'm going to look at those on Wednesday, I'm probably going to be buying 2 of his bikes. If I can't change the shifters for less than $100 I'd rather not mess with it and just use this bike for biking to school (I don't trust a lot of people at my school, no way I'm going to leave a carbon bike there). Would doing this cost me more than $100?

Stem shifters (used) can be found for around $20. If you have a co-op nearby, you might be able to get a set free.

I paid $80 for Silver bar ends. They are lovely. Velo Orange se

You will also need some cheapo downtube cable stops, which your LBS might give you if you ask nicely; new pairs come with Shimano brifters.

If the shifters don't fit your bars, take the opportunity to swap out your handlebars (local bike co-op is your friend) and get new or lightly used aero brake levers (they work better).

All told, you could do this for not very much money (~$100).

Don't bother with stem shifters. I find them more difficult to use than downtubes.

Another option is indexed downtube shifters and an index-capable RD and freewheel; you could probably get NOS 6-speed 105 or 600 downtubes quite cheaply, get a 6-speed Sunrace frewheel, and use the cheapest modern derailleur you can find (such as Shimano 2300 claw mount version). Depending on how nicely eBay smiles upon you, this could be a $40-60 conversion.

Indexed downtubes could help in your case because (at least in my experience) well-tuned indexed downtubes are very easy to shift, and take less concentration than friction downtubes. I still like friction downtubes, but I understand your concern.

Some people find it easier to hold the bars on top, closer to the stem, when they're first getting used to DT shifters. Even better when a bike has dual-pull brakes, as yours seems to have, if it's identical to the eBay ad. I've only had bikes with DT shifters, so I find it much easier to shift off the drops, than by holding the bar on the hoods or the top.

Sunrace makes nice and cheap friction front/indexed (6 or 7 speed) rear stem or downtube shifters. I bought them from Amazon and they come with cables. Having indexed may make the downtube shifting easier. The feel is not as good as my Ultegra 8 speed bar ends but for less than 20 bucks on an old bike its a nice upgrade. The nice thing that I like with the downtube is the ability to shift both front and rear with one hand, rather than alternating hands/shifts with the bar-ends. The actual product looks a lot better than the picture at Amazon.