I just got done installing an autometer tach on my 98 contour. It went fairly easy, and if it was me, I would do that instead of changing out the whole cluster. Easier, and then you won't have to deal w/ the milage stuff!
Wijn
1998 tour Zetec
B&G springs cut 1"
17" Amp "tech-9" rims
Pro tint
2 1/4" exhaust
Autometer tach & Euro Guages
CTA/weapon R combo intake
Zex Dry Nitrous kit