Remove engine from car (far easier than trying to do it insitu).
Remove sump.
Remove big ends and main caps and look for wear/grooves/damage on the crank. Ideally, remove the crank and check journals for wear.
If no damage, simply rebuild engine with new gaskets and shells.
If there is damage and a regrind will solve it (and there are undersized shells available - they aren't for my son's 33), remove crank and get it done. Rebuild engine.
IF you have never done any mechanical work then I would suggest you buy a workshop manual and read it thoroughly and understand it before you start spinning the spanners
Joining an Alfa club would be helpful.