Try using "stick to trimmer" mode on an easily accessible button. It's much easier to finagle that way, and you can trim it pretty well after a bit of practice. You'll get lots of practice if you fly it frequently. Autopilot does sort-of work, IIRC, but it's tied into the data link somehow. Your nav points are stored in the dlink and I think messing with your dlink can prevent you from entering autopilot or screw with its flight plan.
Unless they've released new tutorials, they're balls and should be avoided at all costs. Your best bet would be the official manual and YouTube tutorials. Keep in mind the strengths of the plane, specifically turn rate and speed. It doesn't climb as well as the MiG-29, it doesn't have the radar of the F-15 or an AMRAAM analogue (MiG-29 gets them, the R-77, aka AMRAAMski), but when I said "35 peak G turn" I meant it. You can disable the flight control system (FCS), then roll & pull almost 90 degrees in a distance little more than the length of the aircraft, if you really want to. Think Pugachev's cobra but at higher speed and sideways. Combined with the helmet-mounted targeting system and high off-boresight capabilities of the R-73 missile, the Sukhoi should never lose a short-range engagement against anything else in DCS. Even without stressing the plane like a madman you can out-turn MiGs, and you can out-turn Eagles without trying.
The Sukhoi and MiG-29 also share an advantage in short-medium range combat with their IRST system, or infrared search & track. It's that bulbous thingy to the front-right of the cockpit that sticks up from the nose, and it lets you search for, lock, and fire upon enemies out to ~10km. The game also calls it Electro-optical, if you look for it in the keybindings. Think of it as a short-range radar that doesn't ping everything in front of you, and you get a good idea of its uses. It can spot, track, and lock targets without any indication to the target, and furthermore you can fire IR missiles with this lock such as the R-27ET and R-73, which also won't alert your target. I think you can also launch active radar missiles with an IRST lock, though the Su-27 doesn't get any actives. The MiG-29 does in the R-77, so you could theoretically launch those without ever turning on your radar.
Take all of this into account, and what you'll find is that Russian aircraft are especially deadly when their pilots effectively utilize terrain masking and defensive flying techniques to get close to their targets. It's possible to spot, identify, engage, and kill a target without them knowing you were there until they're staring at their burning wreckage plummet to the ground. You will be outclassed at altitude, over water, and over flat terrain, but if you can get yourself to within the edge of visual range you have the advantage.