The SVT engine is an interference engine, which means when the timing belt goes it usually takes the pistons, valves, and other good stuff with it. So the belt should be changed every 80k miles. I'm calling these numbers off the top of my head, but I believe parts to do the job run about $200, and dealers typically charge anywhere between $500-$1000 to do it. It's doable for a DIYer, but experience, time, and tools are needed.
The clutch *might* also be a concern at that mileage. Ask if it has had the clutch replaced under the TSB, which was typically performed early in a car's life due to premature clutch wear. Some original clutches last well over 100k miles though.
Check the valve cover for oil leaks (hell check the whole car for leaks/unexplained fluids), make sure the alignment is good, make sure the seller ALWAYS used premium gas, basically just do a standard used car check-over.
As for winter, get a set of snow tires and you're good to go. Very few 15" wheels fit, so go with 16" wheels/tires.
Mine: 2002 Focus SVT: 142k, Sonic Blue, #1654, All Options
Mods: Tom's Tune, Borla, HFC, STS, Painted Machs, Euro Grill, FRPP Springs
Hers: 2010 Focus SES: 67k, Ebony, Auto, Moon and Tune