My thoughts: Start with stripping it. You don't know where you are without pulling off the old finish with stripper. Heavy sanding is not recommended on a refinish as it is too rough on the wood. Put away your sander, it is not needed unless there are major gouges or you are trying to create more work for yourself. The Wood's patina will not be destroyed with stripper, I recommend Strip-eze, use with heavy gloves, an apron and in a well ventilated area. Remove the stripper and old finish with putty knoves and med "0"grit steel wool. When you get to the sanding phase, hand sand only with the grain, start with 80-100 grit, finish with 120 grit. Sanding finer will polish the wood and the stain will not lay down evenly. Then stain, I am partial to water based stains if you use varnish or shellac as your protective sealer, oil for Laquer. The stained wood will look flat and dull after staining, do not sand- start putting on the varnish, do not sand out debris or imperfections in the varnish until your 2nd or 3rd coat, you do not want to sand through the stain to bare wood, it will make the color uneven and look bad. The key to a good top coat is sanding the coat underneath with 320 grit until evenly dull (do not touch hard edges at all), wipe with your clean, damp hand and then a wax tack cloth. Make sure the finish is at least 65 degrees so it will flow and level well. Sitting the varnish can outside in the sun for a half hour before opening it, it should have the consistency of warm, not hot, maple syrup. I recommend marine interior varnishes (z spar, Petit, Interlux West Marine brand- Minwax in a pinch), satin only- gloss is for exterior only. Why these marine brands?- they are higher quality and have better flow characteristics, so the brush marks go bye bye and you look like you went to college for this stuff. Brushes are a debate a mile long, I hear everything from foam brushes to badger hair- the key to a good brush is how you dip it, seriously.. I use chinese bristle, it is like the middle road, I place more emphasis on the fairing of the undercoats and the kind of varnish, good varnish makes you look like a pro with little effort, remember Varathane is for floors and bar tops, not furniture. Stir varnish, do not shake, bubbles are your enemy. A good varnish job is 4-6 coats, depends on how much grain detail you want in your finish. You will be amazed how quickly the last coat dries when sanded with 320 well before applying.
My credentials? I have a boat with varnished teak (15 coats), and a house full of restored antiques.
Hope this helps.