Not a stupid question...
I looked at the DSL line-up on the Marshall website, and they are very good at confusion! They show a picture of the "JCM2000 Dual Super Lead", and they list 3 models of the DSL series and their specs, but they don't show the specs for the 2000. Add to that they aren't all the same, patching-wise. Hmmmm...
What you need to patch the Triaxis into the Marshall is a suitable "line level" input on the Marshall that accesses the power amp section. A "series" type of effects loop will let you do this, using the "return" jack (input). In most cases, this type of input interrupts the internal signal going to the power amp from the preamp. A "parallel" type effects loop mixes the internal preamp signal and the external effects return input, so this is not the best way to do this. Problem is, some of the Marshall DSL models use "series", some use "parallel" effects loops, and yours isn't even listed! So what you need to do is consult the rear panel (or the owners' manual) to see what your model has. Series=good, parallel=bad (as far as plugging in an external preamp).
The alternative is to have a QUALIFIED amp tech add a suitable line input to the internal power amp. It shouldn't be too difficult a job...
And before you ask, I would not recommend plugging the Triaxis into one of the front panel inputs on the Marshall. And that's even if the Triaxis has a dedicated "to guitar amp" output (like my V-Twin has). You're just getting too much gain and tone control ciruitry in the signal path. This will suck the tone right outta your axe, and add so much noise, you'll sound like Niagra Falls!!
Good luck, man!

I really believe in the KISS principle, keep it simple stupid.

And Murphy's law, who I feel was an optimist.

It's OK to do things like that in your house or practice under/in controlled environments. In the real world of gigging, if something can go wrong it will. Like a bad cable messing up the sound, ground problems when connecting things. Same for recording, KISS, lots less time tracing down that bad cable.

If you dig the sound, that's it, cool. You want a Boogie, get a Boogie. Once you start trying to bypass the preamp and use just the power section you run into all kinds of mismatch problems. You usually end up wasting money when you have those great ideas. if I hook this up to that and then do this I'll get this, it usually never works.

If you can pickup a used one and sell it at without losing money go for it. If you don't dig it you can at least get back some of your investment.