Check it has had the 12k service done as this is a biggy,valve clearances etc.It will require a service at 18k as well.The head bearings can be checked by pulling the bike over on the sidestand,clearing the front wheel of the ground and getting a mate to check freeplay etc on the headstock ,my own has 17, 500 a 2000 model is still in great condition so the 99 should be similar,worth checking all the engine casings for drop damage,a great bike hope its good condition and welcome to the triumph clan,good luck.