I always do them with front cover on. Before dissemble I mark lines on cam sprockets & add better marks for crank so easier see all good, if you follow service manual on chain links etc it pretty easy set-up although could of been easier if sprockets had proper decent mating marks from factory.
Lots of debate on what do with HG sealing around chain housing lip.
a lot comes down to type of gasket used & what finish work done to block, if in doubt a very light smear bottom & top can be used, keep it very minimal & slightly away from inner edge as will go everywhere if too much & you don't want strands of sealer inside engine that could lead to trouble.
I've used it at times when HG or block bit worrying, used Apexi & Tomei on good finished blocks & heads without & never had an issue although the coating on those mls gaskets is above average.
If in doubt use a bit as better than having an oil weep, just do very light smear though as only trying fill any super slight surface imperfections in chain cover lip & meeting points to block.