yes, it should be that simple.
Presume these are PATA discs, so yes get the jumpers right. Sometimes I have come across bad connectors so if you have ongoing problems check the power molex is OK (touch disk housing and check for 'hum'). 'Icy Box' enclosures are cheap but why not just install the drive as you intend to. 250Gb as a new drive seems a bit small for these days !