olderbenzlover

I am new to this, so please bear with me. Currently driving on the original 15" Wheels & they're not pretty. Would like to move up to a 16" or 17" wheel if possible. What offset would I need & would there be any modifications required ? In a nut shell what specs should I be looking for in a new wheel so that I can be sure they will fit & not do any damage to the suspension or steering. Thanks in advance, D