I think that anyone who puts to sea these days without GPS is at best being perverse and at worst dangerously stupid. If you enjoy astro navigation, then by all means just carry a hand held GPS, with plenty of batteries, in your grab bag for emergencies. But do carry one. In heavy seas, it is very difficult to get an accurate astro position unless you are very experienced. In cloud or fog, of course, it is impossible.
Equally, I would recommend that you learn the rudiments of astronavigation and carry a sextant and the associated tables. But many people will carry a second, or third, battery powered GPS as their backup instead This arrangement will probably work OK in anything short of a lightning strike. Incidentally, during our Atlantic crossing, we were caught in a major electrical storm with lightning bolts crashing down on all sides. Fortunately we didn't get hit, but to protect the GPS I put it in the pressure cooker and sealed the lid, hoping that this would act as a "Faraday Cage". It seemed like a good idea at the time.... Does anyone know whether it would have worked?
We took a Garmin GPS45, which was (and is) excellent. I believe it has now been superseded by the GPS12XL which is by all accounts better. We mounted the GPS on a swing bracket just inside the main hatch, so it can be swung in for use at the chart table, or out for use from the helm. It is connected the main 12 volt power supply on the Nav Instruments circuit.. Initially we used the small swivel aerial, attached to an extension cable and mounted on top of the coachroof. When this got broken, we got a proper external aerial and mounted it on the pushpit, which is what we should have done in the first place.
We also both went on an astro course before we left. This course was very good, since over one weekend it taught all the rudiments of taking sun and planet sights and performing the necessary sight reduction calculations. I already had a cheap plastic sextant, which I took to the course, but this was very difficult to use compared to the metal instruments, so I bought a proper metal sextant shortly after. It is an Astra 111B or something like that, made in China. I think it cost me $200 or $300 in a chandler's sale. It has excellent optics, zero index error across the whole scale and is a pleasure to use.
We practise taking sights occasionally, but the only time it has been used "in anger" was between Laxe and Bayona in Spain, when we had broken our GPS aerial.