Pics are helpful in something like this. What you consider excessive rust may well be nothing but light surface rust that in no way impairs use. OTOH, it may be so rusted that it really isn't worth saving it. The repairs you mention are nothing that doesn't get done to every used bike I buy (well, minus cassette), regardless of how good they look.
As @
Flip Flop Rider mentioned though, it is unlikely that paying someone to do the work will be economical.