Originally Posted by TurbineBlade

Have you ever used friction shifters before? Read here if not: http://www.rivbike.com/article/components/shifting

Honestly - upgrade as little as possible and just ride the crap out of it. Upgrading from cottered cranks, steel wheels, etc. is really expensive and not worth your $ on that bike. If the tires are cracked or worn, maybe get some new ones. Go buy a front a rear blinking light - that's about all I would do.