It depends on what has been done to the home since 1985. You must spend good money to get good money back. What does that mean. There are certain renovations that will bring you more money back than others. Getting rid of wallpaper and old paint jobs always cost less than what is in the mind of a buyer, therefore that should be done. Newer appliances help. Getting rid of the old shag carpet is a must. Connect with your favorite Realtor, ask them for advice on what you need to do, and even a recommendation for their contractor, get estimates and go for it!.
If it is fine looking as you say you might not have to spend much. If you need more work it can be expensive.
A new full bathroom could be $10,000. A kitchen can be replaced for $25,000 to $70,000 or more depending on what you choose to put in there. If you are selling, no need to put Wolf appliances.