I've never brought back a savage engine from the dead but quite a number of other 4-stroke and 2-stroke engines so if it was me this is what I would do.
First, I guess we can assume the previous owner did not prepare the bike in anyway for being stored but just pulled in the garage and parked it.
Now would be a really good time to seal the rubber plug - just by going through the procedure you'll get a chance to check out and lube a lot of parts that need it and you'll get a general idea of what the engine looks like - as in - how much flash rust has built up. If your real lucky the tank is full but I doubt it. After you drain the tank - take a flashlight and eyeball the inside of the tank the best you can looking for rust - if there is very much no amount of fuel filters are going to work for long - but a multi-step tank sealer on the market does work well - expoxy based if I remember correct. I would expect your rubber plug to be ok but the new style one sounds like it should work better, either way seal it as laid out and get a light coat of motor oil on everything you can see that moves in the topend - some folks use grease on the cam - but after breakin just motor oil has worked well for me in other applications. After you get the headcover back on I'd at least pull the float bowl on the carb and clean that out - you may end up rebuilding the carb but maybe not. Cut the fuel line someplace and install an inline filter. Pour about 1/2 ounce of light motor oil like a 0w-30 in the spark plug hole, leave the spark plug out and roll the bike around a bit in gear - were looking for a little coat of oil on the cylinder wall, after you have replaced the battery I'd spin it a bit with the starter - sparkplug still out and a shop rag over the plug hole to catch the oil. Replace the sparkplug, fuel tank and such, make sure it's not in gear (started a Ford Bronco after an engine swap one time in 1st gear - dang thought it was in park - quite an event chase'n it down to dive in the window

) and give it go - real important to let it just idle awhile without cracking the throttle open - it's hard not to - but let the oil build up.
I'd change the oil and filter after about an hour or so of running it.
Use fresh gas of course and the tires/brakes need looking into.