For that locomotive, you don't have to do a total replacement. Go to ERR at This Page and order the following item.
Cruise Commander M Kit - Steamer kit (all versions)
It's a fairly simple install and you'll have 100 speed steps and no more Odyssey Lurch.
Of course, if you want some other Legacy-Like features, consider adding my Chuff-Generator for 4-chuffs/driver rev and optional ground lights. Then you can use my Super-Chuffer to give you great chuffing smoke, smoke at idle, Rule-17 headlight operation, and automatic cab light control.