I just bought a 97 Bonneville SE, and it had two problems.

First P1406 which means I have to replace the EGR valve, okay almost 200$ down.

Now my second problem is that the gas gauge isnt reading. I fill the tank full and the needle always remains at 1/4th once the needle goes below 1/4 I know its starting to run out of gas

How do I go about fixing this? Also how much is it going to cost?

dont replace the EGR right away.. try cleaning it first...

you might just need a new sender for the fuel problem

How would I clean it without messing up? Do I just take it off and put it in some carburetor cleaning liquid or some WD40?

Edit: Never mind did a search and read some posts

Your fuel level sender is bad. Very common problem on these cars. It costs about $300 for the GM replacement.