Oil Change

I assume it is the paper insert type where you have a large o ring to seal the filter cover and a small o ring under the central bolt head? Both need oil before installation and tightening. Not too tight!

 

As above.
If you separate the central bolt from the filter cover you will see where the small oil seal is. Roll it out and roll/slide the new one in.
Their appears to be two sizes of filter cover sealing ring. My '95 Trident 900 has a hexagon head drain plug which is paired with a slightly smaller and thinner rubber seal for the cover (the crush washer for the plug is of a type used on older - 1980s? - BMW cars). A 'normal' drain plug, which requires a spanner, has been paired with a filter cover which, I believe, requires a slightly larger and thicker seal, which is the one that usually comes in the box with the oil filter. Yours could well be the latter.

 

You were asking about a battery for the Trophy. Try a Motobatt. Powerful, reliable and VERY yellow!! I guess that is the kiss of death for mine then!!