That is a real kludge of a 'cassette'. Price set for wheel and 7spd is not at all bad for a shop and the parts you
list are a more than adequate grouping. 7spd should be compatible with your chain/RD and shifters. Ask about
rear fork spacing on the bike versus the wheel your mechanic proposes as the new wheel is likely to be a bit
wider than the old one which can cause minor problems, usually not insurmountable. Ask if the 18 on the rim
is the width. A 32 or 36 hole rim is more than adequate for any use. Old era rims were pretty soft. A new
one should be a lot tougher. Have the chain checked for wear, you might need a new one.

The freewheel (not cassette) is not salvageable, though in theory it is removable you have a very good price for a
new wheel so the hub is not worth the effort, even if Campy though it might be worth something.