Hi and thank you for your post.
In response to your first requirement, bear in mind that digital storage scopes (DSOs) are specified differently to older analog scopes. As well as ensuring that you have adequate input bandwidth for the measurement you want to make, you must also consider the sample rate of the oscilloscope. We would recommend a sample rate at least five times higher than the fastest signal you need to view so, for a 100MHz input signal, you should consider a scope with a sample rate of at least 500MS/s.
There is more advice on choosing an oscilloscope on our website at:
http://www.picotech.com/applications/os ... orial.html
Your second requirement is actually much easier to answer: a digital scope will have no trouble at all displaying the signal from an external RF spectrum analyser. If your analyser has a trigger output which you normally connect to the external trigger of your benchtop scope, simply connect it to the external trigger of a PC scope and select an appropriate timebase to get the whole spectrum displayed on screen. Of course, a PicoScope PC oscilloscope can itself be used as a spectrum analyser - meaning that for signals within its bandwidth you don't even need the external analyser!