If you do decide to switch to synthetic oil, a couple of quickie oil changes are called for. The new oil will clean out accumulated junk you do not want in your engine. At conversion, I changed oil at 600 miles and 1,500 miles before adopting my regular oil change interval.
For my purposes, Mobil 1 (at Wal-Mart sale prices) is a reasonable compromise between quality and value. I am not convinced that a more expensive oil will significantly extend engine life. I suspect that there are lower cost group 3 synthetics that are better from a cost benefit perspective (for non-turbo engines), but I am too lazy to perform the research necessary to gain comfort with a decision to switch.
20 years ago, there was an issue that Mobil 1 did not swell seals at the same rate as dino oil resulting in post conversion leaks. The Mobil 1 formula was changed to eliminate this issue. If you search the forums, there are stories of engines that leaked after conversion. The theory is that some of the junk you do not want in your engine was plugging small potential leaks. When Mobil 1 cleaned out the junk, the leak manifested itself. I have not experienced this issue, but would encourage observation after a conversion.
The good news is that whether or not you decide to go synthetic, contemporary oils are definitely superior to those available at the time your engine was designed. Adopt an appropriate oil change interval and stick with it.