This is a full tower if I'm not incorrect, I'm planning on putting a 600 watt in there with a power switch, but not sure how to remove the current 460

With so many models we can't really say or even guess what the model is. 

But, if its a full size tower, most within the last 10 years use standard ATX power supplies. 

It should be fairly self explanatory how to remove and install a new one.  The only issue is most Dell's do not have a power on/off switch and you may have to make a hole to accommodate the power switch.  

The only other suggestion is to use a fully modular power supply to avoid stuffing unused power leads inside the case.

If you know the Service Tag (on a sticker somewhere on the PC), go to the Support page and enter that tag. It will tell you exactly which PC model this is.

(Do not post the Service Tag here.)

ATX 20 PIN  is wrong.  EPS 12V  24 PIN 80 percent efficient with 150W combined on the 3.3V 5V RAILS.

Size also matters as the top usb ports will not allow a unit that is too long.

EVGA 750B1 works fine.  The  B2 B3 BQ G2 versions from the same vendor DO NOT WORK. There is a reason why the G1 is $250 and the B1 is $120.  B2 ETC ARE UNDER $100 and some FAKE units that claim 750W are $29.  The B1 is preferred due to price but BEWARE of any unit that claims 750W and is UNDER $100

https://www.youtube.com/watch?&v=2s0QP4cAecg

https://www.amazon.com/EVGA-SuperNOVA-Modular-Warranty-120-G1-0750-XR/dp/B00K85X2A2/

https://www.amazon.com/EVGA-SuperNOVA-Modular-Warranty-110-B1-0750-VR/dp/B00K85X23O/

EVGA SuperNOVA 750 B1 110-B1-0750-VR OR G1120-G1-0750-XR

750B1 installed in XPS 8700

 750B1 LABEL

 750G1 LABEL NOTE 150W combined 25A on each rail.

Based off the site, it's a XPS 8300

8300 8500 8700 use same case design with the Top usb ports getting in the way of longer power supplies.

The recommended unit is due to physical size as well as power output on the 3.3v/5v rails combined.

Power supplies are not a single voltage nor a single spec of watts.

All the rails are required.

This is what the XPS 8300 looks like with the cover taken off.

XPS 8300 INSIDE VIEW

 NOTE the TOP USB Ports will BLOCK a power supply that is TOO LONG to fit into the case.

Tight Fit but it DOES Fit

700 B1 is the smallest that works.

600 B1 does not have enough 3.3v/5v power.

https://www.amazon.com/EVGA-BRONZE-Warranty-Tester-100-B1-0700-K1/dp/B018JYHBE6/

Again B2 B3 BQ W1 G2 versions from the SAME vendor Do not work for the same reason.

130W NOT ENOUGH

150W combined

Yes, I plan to put a EVGA 600 B1

So this one will work? https://www.amazon.com/EVGA-BRONZE-Warranty-Tester-100-B1-0700-K1/dp/B018JYHBE6/