Huge amount of work, and will cost a small fortune. But all doable.
Mechanically, pretty straightforward. All bolt-in with the right combination of parts. You'll be tearing the car down basically to a shell, but with some organization and patience, just a matter of bolting the new parts in place. Obviously the engine and transmission have to come out, but the entire dash, as well. It will be a big paperweight for months, possibly years.
EJ207 is a turbo engine, considered one of, if not the, stoutest (Vermont Sportscar uses only EJ207s in the Subaru Rally Team USA cars). The smaller displacement means they rely more on the turbo for power, which means less power in the lower rpms. But a tune and turbo sizing will help get the results you want. It was never available in the USA, we got the larger EJ257 here.
The 207 was made for ~20 years (I think it was exactly 1999-2019), so even with that specific engine code, there are a myriad of details that surround the swap. The easiest and cheapest way for a novice to do this job, is to get a complete donor (half cut from Japan), so you have all the parts that you know all work together. Sometime around 2005, these cars would have gotten an immobilizer, which will make it considerably more difficult to get the stock ECU to run it (assuming you use the stock ECU, a standalone would yield some better results, but bigger hurtles to get there). EJ207s were only in Imprezas, which never got the rear suspension that's in your Outback, brakes will bolt right up to the Outback suspension, axles get a little ugly if you want to use an r180 rear diff instead of the standard r160, but still doable.
The vast majority of EJ207s will come with a 6-speed transmission, which is a much better transmission but will add several thousand dollars to the purchase price. I think all 207s were mated with the r180 rear diff.
This is all assuming you stick with the EJ207. Almost any engine made by Subaru in the last 30 years can be used in there with the right combination of parts. Turbo 4 cylinders, as well as several 6-cylinders. These projects have been done hundreds of times in BE/BH Outbacks, and probably tens-of-thousands of times in other Subarus.
Anything turbo will require a turbo engine crossmember.
None of these options will effect your tie rod ends. If you need them, replace them. Depending on the condition of your CV axles and timeline for this project, I might not wait on those.
The manual swap isn't too bad, but if you're serious about the engine swap, you'll save yourself a lot of headache to swap the manual pedal box in when the dash is out.