Here is the exploded view from http://hoseeker.net. Your description is a little vague. Are the side rods or valve gear coming apart? Is the rear engine not completely attached to the boiler? See if you can tell from the parts list.
(Click on images to enlarge.)
Nelson
Ex-Southern 385 Being Hoisted
I fixed up several Rivarossi steam locos a few years back. Golf Manor Hobbies in Cincinnati had all the parts and Rivarossi diagrams I needed for each. Last time I was in Cincy about a year or so ago they were still in business. Telephone: 513-351-3849.
One of the engines was a cab forward. In that case, I only needed to buy some detail parts. The main repair I made to this loco was to super glue the broken frame back together. The frame was broken at the rear cylinders causing the mechanism to bind up on one set of drivers.
GARRY
HEARTLAND DIVISION, CB&Q RR
EVERYWHERE LOST; WE HUSTLE OUR CABOOSE FOR YOU