You can cover that red window with a slip of aluminum foil and black electrician's tape and it should work for IR film. A good source for the film is Freestyle which carries a lot of photographic film products.
One issue you might run into is focusing. IR light focuses differently than visible green (the latter is used as the standard for most lens designs) so if you use the reflex focusing screen, you'll be off a bit for IR. Focus using your viewfinder and then nudge the focus a bit away from the infinity end (some lenses have an IR mark which is used for the offset). Then put your IR filter on and shoot (you need an IR filter over the lens and a lot are available on the internet - just google "IR lens filter"
Sample IR filter listing at B&H.). Otherwise, shooting at a smaller aperture and making use of the greater depth of field will help with getting a good focus. Trial and error works too.
Most IR film requires loading and unloading the cart in the dark since the lip of many carts allows IR light to get past. That makes it an issue for a lab unless they're familiar with IR film. Many B&W developers work for IR film so no issues there.
Exposure is something you'll have to play with also.You'll probably be making manual exposures with IR film, so the DX code issue is irrelevant because you will be overriding the camera's exposure setting anyway. You can use the rated ISO for the IR film as a starter, but you'll usually end up adjusting your exposures based on experience. IR film is not hard to develop yourself - just like regular B&W film in all respects except you need to avoid any IR light sources (remember YOU can't see these). Some changing bags are out since they transmit IR light so it's best to unload & decapitate the cart, and load your developing tank in full darkness. You mentioned a stainless steel tank which is ideal for IR (plastic tanks sometimes transmit IR light). Once the film is in your tank, it's just like any B&W film from there on out.
I second jatrax's suggestion on using a converted digital camera for IR (if you get serious). A used K-01 is a good choice, and it's autofocus will work with IR quite well. You can see the IR image on the rear screen, and a DSLR will go further into IR than film (plus with an IR/UV blocking filter, you can use the converted DSLR as a regular camera). You can be spot-on with focusing and there's virtually no grain with an IR DSLR compared to film. Used K-01s are available on eBay and elsewhere, but be sure you read the fine print if you buy.
Isaac Szabo is a good resource for having a K-01 converted (there are others).