[RickM]

Alot of good advice here. I had a two layer roof rip and replace when I bought my ranch several years ago. Luckily a family friend was in the business and he did the entire job complete with GAF brand - Cobras ridge vents. He also doubled up on the rubberized ice shield (obviously not an issue for you).

My advice would be to get references as suggested and look at the homes that were done recently and perhaps 5-10 years ago. The reason to question older jobs is to see if critical areas like chimneys, vents, flashings, complex angle joints etc kept rain out. If any of these customers had a problem did the contractor remedy? Many don't like to take the time for "small", time consuming troubleshooting. something to get in writing.

Consider that when a chimney is redressed some contractors slop tons of tar at the seam while others will utilize copper flashing with the appropriate amount of sealant.

While I like the performance of the ridge vent and believe the claim that it enhances shingle lifespan it will likely render a gable type attic/whole house fan useless. At least as far as drawing air from the house windows. All air will be drawn from the ridge vent. In order to complete the effectiveness it is wise to install soffit vents as well.

Will the leaders and gutters get ripped as well? Probably. Consider that saving and reusing is usually not worth the effort.