You are at the point you need to borrow the tools to do the job or take it to the shop for a diagnosis. Myself I would be careful with the low pressure switch as the valve in the accumulator can leak. The second the o-ring comes off the switch you can't screw it back on with it still leaking. By the time you get to a shop the system will be empty.
Minimum tools are the gauges and leak detector. Vac pump can be rented.
Don't use the high side valve unless you have to. And then expect to replace it as debris from the compressor will make it leak or heat and age ruined the seal so it will not reseal.
Some shops will credit you for 134A recovered. So a diagnosis and recovering the system can be worth the money. You change the parts at home, suck it down and recharge it. Again a leak detector is very useful to make sure repairs are good.
