"being a noob, and diving in head first with a 100L barrel, im concerned that i will mess it up"....I'd say you should be kind of concerned with just this much. Barrel aging is kind of looking for trouble if you don't have a couple batches under your belt. Adding an experimental fortification and solera system for what _sounds_ like your first batch is asking for trouble. I'd strongly recommend any noob start by doing a few kits in carboys first. If you want "barrel flavor", get kits with oak or buy a pack of cubes. Cheap and easy. Most decent kits are actually pretty good even _way_ young, and they're pretty foolproof and let you get a solid feel for the process. Sure most get better with age, but a kit gamay 5 weeks off the fedex truck is pretty much my dad's all time favorite wine, so don't discount young kits till you try them. I say this having recently thrown 2.5 cases of my first round of juice buckets into the dumpster. It hurt. But it would have hurt a lot more if it had been 10 cases plus a ruined barrel. Or if I didn't have another 15 cases of 10 different varieties that I've been happily drinking while waiting to see if a year or two brought that one bucket round. I've done some pretty experimental batches in the intervening time, so I'm hardly saying don't experiment, but maybe a 3 or 6 gal carboy is a better experiment size?
Are you a big madeira fan who really likes that oxidized flavor? If so maybe try oxidizing a commercial bottle of shiraz plus a few shots of vodka so see if you like the results, 'cause I'm pretty sure oxidized shiraz tastes nothing like madeira. If oxidized shiraz isn't your goal, then to reliably get non-oxidized wine, you need to sulfite _every_ time you open the container after fermentation is complete(wine dissolves oxygen in minutes but takes days to react with it, while sulfite reacts/destroys dissolved oxygen in hours). The legal limit for sulfite in commercial wine is 350 mg/l. Doesn't apply to us, and it's probably a super conservative limit, but in excess it'll still give your wine the aroma of burnt matchsticks, so you can't just go crazy with it. If you want non-oxidized wine you can drink whenever, it's _way_ easier to just bottle it.