I don’t think SS lines were ever OEM on the LT, but no matter as long as you have them you should be good to go for a long time. 77K is nothing for an LT. Mine just rolled over 96,000 and runs better than ever.
I could concur with Dean and suggest a complete 24K maintenance cycle since you lack service history. The 24K goes through fluid and filters pretty thoroughly and things like a valve clearance check and adjustment if needed. A few things to consider that aren’t in the BMW maintenance list are lubricating the shift linkage, lubricating the centerstand pivot points (a real PITA) and replacing the fuel tank quick disconnects if they still have the plastic parts, the male plastic part in particular.
And ensure the battery is good as the LT does weird things if the battery gets low as I found during my last brake fluid flush.
As for oil, you will get a hundred different recommendations. Many will say car oil is fine since the LT is closer to an auto configuration than are most bike since it has a separate transmission. However, it is still a high output, high revving, solid lifter engine, unlike most modern car engines that rev less and have roller tappets, so it needs the high pressure capability of things like ZDDP, which has been greatly reduced in modern auto oils. Personally, I stick with Castrol motorcycle oil as it contains a sufficient amount of this compound. Some of the auto oils such as Mobil 1 15W50 apparently still have significant amounts since this oil is not recommended for any modern car, but I still pay the extra for motorcycle specific oil to be on the safe side.