A SDR at the first IF is really neat. It can be used as a panadator for the RX, although the SDRs display gets a bit woozy as I tune. However, you can see a large section of the band with the SDR and all the little signals that are swamped just using audio. The SDR can be used indepentently as a rx and tune within the first IF; basically using all the good front end of the RTX that the SDR doesn’t have.
The address for the 1st IF isolation amplifier I used is http://www.cliftonlaboratories.com/z10000_buffer_amp.htm. It gives details for fitting the amplifier for other TRX including FT-1000MP. When purchasing, You need to specify the gain of the amplifier, usually unity, as the signal should be fairly strong once it gets to the first IF. Delivery from the USA to Australia can take 3 weeks, ask how much extra for faster delivery.
Another way is at http://www.w1ghz.org/small_proj/small_proj.htm, about halfway down. It includes a filter to remove the local oscillator, and a further article that uses an opto-isolator to turn the SDR off during transmit. I had been looking for this site as I wanted to add both the filter and switch, having bought the parts to do it. The Mini-Circuits parts are available on special order from http://www.minikits.com.au/, as are many other interesting bits; he makes up patch cables to order too. There is another article on 1st IF taps that uses an in-line Mini-Circuits filter, which is easier to do, but I haven’t been able to find it.
The cheapest SDR to cover the 1st IF is just a RTLSDR dongle from ebay. You can get them on eBay for less than $20. Try to get one from an Australian store, otherwise you will be waiting weeks for delivery. I could only find one this morning: http://www.ebay.com.au/itm/USB-Digital-TV-Radio-for-PC-DVB-T-DAB-FM-SDR-Receiver-Dongle-RTL2832U-/331059172700?pt=AU_Components&hash=item4d14aa155c. Just search eBay for “RTL2832”.
These dongles go down to about 60 MHz, just enough for the 1st IF.
The other one you can use is a Funcube Pro+, but they are from the UK and more expensive, ~AU$200 although are plug and play. I use one of them.
For software there is SDR Console, HDSDR, SDR#, and CuteSDR among others. There is a site devoted to RTLSDRs that cover all of these and more: http://www.rtl-sdr.com/.
For a panadapter, SDR# is probably enough. See http://www.rtl-sdr.com/rtl-sdr-quick-start-guide/. Use the latest version of zadig: http://zadig.akeo.ie/. If using Windows 8, as I do, there is a special start-up mode for installing non-signed drivers. Windows 7 just gives a warning.
It can be tricky getting the RTL dongles driver and associated files installed.
Added 9 Jan 2014
I have snipped parts of the block and circuit diagrams to make it clearer where the 1st IF tap is and how it seems a reasonably safe place to put it.
However, a word of caution to others wanting to modify different TRX for a panadapter. The IC-7410 is a very different design to other radios as much of the circuits for Rx and Tx are not shared. The best place for a panadapter is before the roofing filters if they are used. Unlike older superhet designs, the 7410 generates SSB modulation in the DSP, not through a sharp skirt filter (typically 9 MHz or 455 kHz). As such, taking an IF tap near the main SSB filter of a conventional TRX is very different as the RX and TX paths are shared, unlike what is done in the 7410.
The tapping point is most clear in the circuit diagram of the 1st Rx mixer and the last Tx mixer, as they are clearly separate, plus there is a test connector to plug into. There is possibly no need to switch the isolating amplifier out when in Tx, but the bandpass filter could still help remove the local oscillator, but it should be minimal as a balanced mixer is used. It may be possible to just run coax out of the TRX and have the isolating amplifier outside.