Yes, sometimes you may need a bit of silicone as there can be slight variations in the LED size.
We recommend leaving your lights up to enjoy them year round however if you do decide to store them it's best to get the panel out approx once every month or so to ensure the batteries are kept healthy.
This product uses LEDs which are soldered to the wire string and are not replaceable.
The panel needs to be facing the sun for the most amount of time over the entire day. Mid day sun is of course the strongest. Depending and where you live the angle of the panel will change over the year. Right now in the UK the sun is almost straight overhead thus the panel should be almost horizontal at this time of year.