If it's your only car, an engine swap will have to be well planned and very well executed in order to avoid a ton of down-time during the swap. In all honesty, unless you're planning to crack open an engine and do a headgasket job, you're better off with a 1JZ-GTE than a 7M-GTE. Odds are better that the 1JZ will hold strong than a stock 7M. Almost any and every 7M-GTE that you can buy will be layered in question marks as to how long it will last. It will help to do the basic things like clean your rad to keep it efficient, flush the cooling system, replace the valve cover seals, the trouble hose on the back of the head, and retorque the headbolts... but when it comes down to it, the headgasket could already be on it's way out. Unless you're prepared to crack open the 7M and fix things before they break, JZ that thing.
The 1JZ doesn't normally have headgasket problems due to its MLS factory headgasket. It's an entirely different animal to drive however, so take that into account when you're picking and choosing.
In terms of cost, doing a 1JZ swap vs a 7M-GTE "stock restoration build" is about the same price. If it were me, I would build the 7M-GTE over a 1JZ because it's driving characteristics are much more suited to the MkIII's girth around town. A 2JZ is a big step up in cost from a 1JZ for the purchase of the engine.... but both require about the same amount of work to install. The 1JZ is a smooth revving powerhouse design, as opposed to the 7M which is more akin to a tractor motor.
A 1JZ cut typically costs $1500 as a median price. A 7M-GTE can be had for 100-250 bucks. I've seen several go to the dump, infact... could have had them for free. That would leave you plenty of cash to take it apart, deck it, check it, new bearings and seals, and bolt it back together... before you've even purchased the 1JZ. A used harness, ECU, and various other bits can be had from people parting their cars or wrecks at pick-n-pull.