OK, if you're happy there's no bridges, fair enough.
First attempt, you just want to see if the power LED turns on before you turn off quick.
No rising pillars of magic smoke? No fishy smell? Turn it on and leave if until you get a boot screen.
The reason I wasn't happy with the U34 cap was the big ball of solder looked very dully. Very dry, not properly melted.
Usualy a switch has zero resistance between the middle pin and one of the outer pins, flipping to the other when you flick the switch. Easy enough to check with a multimeter, don't plug it in when you test it that way.
Do plug it in the right way. Upside down it will fry your Amiga.
If you're going to do more of these, do get some real lead solder (look for Pb included), you can find small lengths of it on places like Amazon and Ebay "For DIY use".
All about practice.