You don't need to uninstall anything related to FSUIPC. You should install version 4.10, but it doesn't matter if you do this before installing SP1 or after. FSUIPC will not crash FSX SP1 nor will any of its needed files get destroyed by installing SP1.
The DLLs which are certainly not compatible are those related to the SDK. f you installed the SDK with its modules such as the Traffic Explorer, then you should install SP1, then install the SDK SP1A update before running FSX again.
I understand there are some other third party DLLs which might cause problems unless updated -- FSCopilot, possibly, for example, but I'm not sure of the details. Anything only using FSUIPC will be okay.
Oh, I don't think you need worry about 3rd party aircraft either.
Regards
Pete
Perhaps this is a VERY stupid question - but it does not appear to have been answered anywhere else.
Is it necessary to UNINSTALL the SDK prior to installation of the intallation of SP1 followed by SDK SP1A?
I find TRAFFIC EXPLORER so useful it is a program I could not (easily) do without.
Ian C