Best thing for securing that bike is a front wheel chock. I have several, my preference is the Condor brand. You can use it on a variety of sized wheels, front or rear tire. Once pushed in, you can even strap the bike to it for added safety.
First order of business is to buy a proper set of JIS screw drivers. ALL the screws on that bike are JIS, not Phillips. That's why several are stripped; some ham-fisted PO used a Phillips. And every nut and fastener is metric, so proper set of metric tools too.
Any steel screw or bolt going into aluminum needs Anti-Sieze applied to prevent corrosion. When you buy your JIS drivers, you also should buy an Impact Driver. That will break loose any screw with little to no damage.
Good luck, have fun, and take your time-