2003 navigator tires?

hey guys, i have a 03 navigator with stock chrome rims. the chroms is peeling off and now i have slow leak on all my tires. my stock rima size 18x8. i was wondering if i could use a different set of rim, 18x7.5 alloy rim not chrome. im trying to get rid of my chrome rims. thanks ps will my old tire still fit with the 18x7.5?