You will need the left side cover gasket. No gasket gunk from a tube should be trusted. It is a smart idea to replace the seals while you are in there. The drive shaft the front sprocket is on has a seal where it exits the internal engine and also a seal in the side cover you remove. The shifter shaft also has a seal where it comes out of the engine. All three of these oil seals might be fine but it is good insurance to replace them.
I would not attempt any of this wrenching if all I had was the on board tool kit at my disposal! Not saying it can't be done but you are opening a can of worms and I highly suggest you have a good tool box with you if you run in to problems. Also, make a template out of cardboard and trace the pattern of the new gasket on it. As you remove each side cover screw poke it in to the corresponding hole of the template so you know where each different screw gets returned to.
This is a fairly straight forward job but you will need a tool to clean off stuck gasket pieces from the side cover and engine mating edge. Chances are good the the tiny screw driver in your tool kit will not get the side cover screws out. Pulling the seals will be another issue. There is a tool like a cork screw to get them out. I used a tiny drill and a dry wall screw to pull them. Now for my personal opinion on this. Doing all this work and replacing the seals, gaskets, chain and sprockets is best done by a competent wrencher with real tools and if you are going cheap with a stock roller chain rather than an O or X ring chain it is a lot of work for not many miles of insurance. You will be adjusting the chain regularly and wearing out your sprockets much quicker with a cheap chain.
You our can lay the bike on its side and avoid doing an oil and filter change or dump the oil and refill when you are done.