Not Sweet Vibrations

This one has me scratching my head, but then again I do that a lot when it comes to truck repairs. I have a 98 Suburban K1500 5.7 4x4 and over the last few days something has started to happen.
When I hit speeds of 60 and again at 65 the truck vibrates in the front end, and only at those speeds. It also made the service engine light come on yesterday but not today, still had the vibrations at those speeds.
Well never had this happen before, I can build a great home and build a great set of golf clubs but when it comes to trucks I'm lost. Now I can tell you what's wrong and follow directions, so my eyes are open and I'm ready.
I thank you guy's that know these type of things and it's so great to have sites like this for us shade tree mechanic's. Hope to read ton's of input and I really pray that the problem is not major.
Thanks,
Jerry
God Bless