Yes. There's a pretty good search function at the top of the page.
See one of my (many!) CR240 threads on this for my struggles with the BD241. Mine came without the mica insulator, so whenever I had the PSU board in the case nothing ran, but did as soon as I had the board out. I now know because the transistor was isolated from the chassis, whereas connected without the mica washer it was grounded and shorting out.
The metal standoff goes to the copper ring on the upper of the two screw holes. The nylon is the lower. The BD241 has a mica insulating TO220 washer between it and the case, and an insulating standoff between the heatsink and the board so the screw doesn't touch the transistor's heatsink.
I don't know about your LED problems. Mine were far too bright, so I had to keep increasing the current limiting resistors above what I'd calculated.