mountain bike chainsuck, replacing parts while thinking of future upgrades
Sounds like you are going to be replacing the middle ring. 'Bolt Circle Diameter' is the measure of chainring compatibility. You need another ring of the same BCD and you can check the specifications for that on the Shimano website.

Personally I would go for another Alivio ring because they are made of steel rather than aluminium alloy, this will last a lot longer, cost a lot less and the weight difference will be marginal.

The shark-fin look to the teeth is deliberate, they are individually sculpted so as to make shifting that bit easier. The bent tooth is the problem - and the missing teeth.

You can order in confidence from Wiggle and return the item if it is not the one you want, albeit with some postage to pay.

The chainring bolts do need an allen key at the front and a proper tool at the back. See if your big-fat-screwdriver can be used instead of the proper tool - tightening chainring bolts is not an everyday task so you may be able to skimp on getting yet another tool.