Take a look under the bottom step and see if you can find a label with a number on it. You need the number if it is from this company:
Christianson Industries
27328 May Street
Edwardsburg, MI 49112
269-663-8502
For my 01 Diplomat (may be the same for your coach) the number is MHL176 and there is another number of 60556 for the top ladder. The removable ladder is MHL242 - second number 59684/ Tje cpmmectpr tubes are 206200 - 5180. My upper ladder is a 6 step unit. If yours has 6 steps they should be the same.
If the above company does not recognize any of these numbers then try this one:
Atwood Mobile Products
1120 N. Main St
Elkhart, IN 46514
800-637-8938
http://www.atwoodmobile.com/windows.asp