Installing the SVPre requires hooking up 4 wires.  3 of these are solder joints.

The red wire goes to the power.  On my little SV112 it solders to the right side of R-45 resistor.  That location has over 250VDC on it when the amp is turned on.  The other 2 wires are the heater wires and the voltage there is low.  The last is of course the 6-wire Ribbon Cable.  The most voltage on it is what I call pin #1 and is 5VDC.

Once the SVPre is installed and the amp is turned on the back of the SVPre's tube socket is pretty exposed to your hand when you change the DIP switches.  That tube socket - and the other solder joints on that board near the tube socket - has that 250VDC on them.  The actual tube I think maxes at a little over 130VCD or so.  I don't remember.  There is a concern when you change the DIP switches.  You must be careful with the back of that tube socket or you can get zapped.

Other than that - you should-not have your hands browsing around in the bottom of the amp touching the caps and solder joints unless you're like me and always doing mods in there.

If you leave the StandBy switch in the "on" position when you turn off the amp (either by pulling the plug or flipping the master switch) the voltage in the caps (in the amp) bleeds off very quickly.  In the matter of 1 minute it will be down.  If you turn off the amp with the StandBy switch in the StandBy position then you  will  isolate the high voltage in the caps and the bleed down will take quite a bit longer

Even knowing this I never stick my hands in there and touch anything unless I first put my voltmeter on the tube pins and check for high voltage.  Once I do my little check I know I'm safe.  I recommend you do the same.  Then you will know when you are in danger.  And "yes", it is that easy.

The Blue connector:

I took one look at the dreaded blue connector - put it in the trash can - and just soldered the ribbon cable.  I honestly did not want to mess with that thing.   I also had no doubt I could make those solder joints.  lol

Good luck.