A gas engine is easy. Remove plugs and prime bores with something to loosen up any stuck rings - often the case if a non-detergent oil was used - for a few days. ATF might be good.
Drain fuel tank and clean out as necessary. Clean/change any filters and likely clean out the carb, but may not be necessary. Same with engine lube system - drain clean/change and refill.
Remember clutch may need unsticking and the back end will be turning once the engine fires, so don't forget making all normal service checks prior to more than firing up the engine momentarily
Check for rotten water hoses fan belt, etc. Fill and check for leaks.
Probably best to change contact breaker points in ignition (or clean) and check for spark from the system (no need to be turning engine at this point). A new set of spark plugs might make things easier.
Without the plugs fitted, I would usually turn the engine on the starter to see if the oil is picked up (as long as the engine is completely free), or you could pump in some oil under pressure at the oil pressure warning light connection point. Likely other ways to achieve this.
There is some risk of the pot with the open exhaust valve being damaged, corroded or the valve(s) stuck.
A temporary (at least) oil pressure gauge is good to check the lube system, rather than the idiot light. Fast pressure rise, slow fall, correct readings at idle or working, etc.
The above is not necessarily an exhaustive list and you might find an old nest of mud dobbers in there somewhere, wiring chewed through or a multitude of other maladies. The list is too long to account for all possibilities!
You should get a feel for the inner condition of the engine from your observations - plugs, compression, etc
If all checks out as OK, go for it. Start her up.
PS. Oil type used will likely be clear on checking - non detergent oil will appear clean (cr*p will have settled out over a ten year period), but a detergent oil will still be black. All assuming the oil was not changed after last usage!