The 1st was one of three infantry regiments (1st, 20th and 63rd), of the 6th Infantry Division.
At the time of the invasion of Luzon, at 9:30AM, 9 Jan 45, following heavy air attacks, an estimated 67,000 troops landed in the Gulf of Lingayen, on the central west coast of Luzon.
Overall command of our forces was by General McArthur, with Admiral Kinkade in command of the naval forces.
General Kruger (6th Army), in charge of land operations, launched General Swift's I Corps to the left, near Damortis, with General Griswald's XIV Corps on the right, near Lingayen.
1st IR, 6th ID led the attack as part of I Corps.
As you suggest, there was little opposition, General Yamashita, commanding 14th Army, with 262,000 men, deciding against resisting the landing.
However,the Japanese air force remained active, damaging the battleship MISSISSIPPI, the lightcruiser COLUMBIA and other vessels. The battleship COLORADO was accidently hit by fire from other American ships.
On 10 Jan 45, the beachhead had expanded well beyond the 1 1/4 mile wide by 3 1/2 miles deep which had been established on the 9th. The main body of troops were now advancing toward Manila, with I Corps advancing north and north-east, taking San Jacinto.
That about covers your inquiry, I believe.
Campaigns: New Guinea Luzon.
Casualties: Killed in Action, 410 Wounded in Action, 1,957 Died from Wounds, 104.
Let me know if this conforms to the profile you have developed. OK ?