Ok so I bought an old beater with some crap stem shifters on it (Falcon?), they are way too hard to shift. SO I'm thinking a cable and housing replacement will be crazy cheap <$20 and probably very effective.

The only thing that confuses me is the housing is split into 3 pieces. 1 - shifter to downtube, 2. downtube to chain stay, 3. chain stay to derailleur. Each of these pieces has an aluminum cap on it to avoid folding into the holders that each piece sits in.

I can buy long pieces of housing, but I need 3 and I have to cap the ends. How does this all work? I'd make this fix in a heartbeat if I wasn't confused about this... help???