04 Suburban Ticking

I've got a 2004 Suburban with a 5.3 flex fuel v8 with 142,000 miles, and it's recently started making a ticking sound upon start up. About a month ago it started out of the blue. At that time I ran some Sea Foam in the motor for a little bit, then changed the oil later that day. I opted to go with a good quality high mileage motor oil, and at a little heavier weight. This seemed to resolve the problem, but as of today the ticking has come back.

It makes a loud ticking sound only when I start it cold. Once it heats up, after about 5 or so minutes, the sound goes completely away. A close mechanic friend has suggested that it could have bad lifters. Does anyone else have any suggestions?

If the general consensus is that it does have bad lifters, how much does it cost for the parts and how difficult are they to swap out? Can they be done by only removing the intake manifold, or do the heads have to come off too? Any help is greatly appreciated. Thanks for reading!