You need to find out of it is possible to adjust the seat post; is it rusted in or can you move it up and down? Because if it is rusted in then you'll need to get it out; which isn't always possible. Unless it happens to be at just the right height for you already. Similarly with the stem; if you think the reach is too short you might want to fir a new stem if you can get the old one out. Given the rust elsewhere on the bike you'll be lucky if both the stem and seat post come out without a fight.
You need to find out of it is possible to adjust the seat post; is it rusted in or can you move it up and down? Because if it is rusted in then you'll need to get it out; which isn't always possible. Unless it happens to be at just the right height for you already. Similarly with the stem; if you think the reach is too short you might want to fir a new stem if you can get the old one out. Given the rust elsewhere on the bike you'll be lucky if both the stem and seat post come out without a fight.