Your 1988 production GP100 was made in the 2nd year of GP production, and GP's started rolling out of the Ruger plant in 1986.
I recently put a stainless 1989 production 4" .357 GP on layaway, and I am looking for a very early 1986 production blued 4" GP.
Many people feel the older GP100's from the 80's and early 90's had superior fit and finish, but somewhat rougher actions. I don't agree, I have a 1990 production fixed sight 4" GP that is very slick.
I do agree that the bluing on the earlier GP's can be more attractive,since more time was put into the polishing and bluing, but it's not a hard and fast rule.
Unlike S&W, there is no feeling that "older is better" with Ruger revolvers........I have Ruger DA revolvers from as early as 1972, and also a brand new 2011 production .44 Alaskan and the new ones are as top notch as the old ones.
There should be 0 issues with your 1988 GP, it will last forever and is every bit as good as a brand new one.