Hi-scan is a marketing term for trinitron displays with a screen aperture grill able to resolve a 1080x853 resolution. What this means is there is there is moderately more resolution than from a TV with a more basic aperture grill.
I found your TV's manual herehttp://www.docs.sony.com/release/KV32XBR250.pdf
From what I've found online it looks like there is very little chance your TV will accept a HD signal or do anything in HD. But it should do SD really well, better than most of Sony's HD CRTs do at least.
It supports S-video and yPbPr inputs so hook up your equipment via those instead of via composite and it should give good quality.