I don't know that model. I have a 54542A that works fine well past its claimed limit of 500 MHz. In fact I measured around 650 MHz bandwidth, very high for what I do.
Having said that, it's seldom necessary to have a wide bandwidth scope to troubleshoot a receiver. You put a signal in and first see if you have a corresponding IF signal. If not, the problem is near the front end. If so, it's later in the chain. Those radios are almost always at least double conversion so there is a second mixer to investigate.