New rx8, obvious problems with engine

Hi all. Just got a 2005 Mazda rx8 shinka with 95k miles. It's obvious after reading up on the vehicle before I purchased it that it needs a new engine, or rebuild at least. It's suffering from an extended crank time due to what I think is poor combustion from the engine about about to fail. It's also got a hunting idle, both warm and cold. Along with a rattling rattling from from the exhaust from what might be again the poor combustion. The cat was replaced recently so it's alright. Aftermarket exhaust as well. The last problem besides the cel that just came on is the superb lack of power in in the higher rpms. It feels fine until you go to pass, and then feels like like you are driving a four banger against a race car. Leaving you feeling let down lol. My question to you all is, once this engine goes; should I be looking at a rebuild or an entirely new engine? Keep in mind I'm in Fairbanks Alaska so I'm not sure if I'd have great access to engines being shipped here (not sure how that works, if a shop orders orders it or whatnot; I've never had to get get new one). Just looking for for the best solution, and the RIGHT way to do it. I am purchasing an extended mile mile warranty from usaa before before the engine goes so it will be covered when it does. Anyways, that's about all the info I can think you need to know to help give me some advice about my situation. I'm new to rotaries but I have a general knowledge after doing my research, and am moderately mechanically inclined from projects in in the past. So don't make my head explode but don't be afraid to go in-depth either. Thanks in in advance and can't wait wait to have this rx8 running like a rotary should.