yes gas will be lost,
yes vacuuming will be required.
you can contact pakref, they will service without opening the AC. but i dont like their charges. not justified.
you need to be dead sure, its a servicing issue only. in servicing, only the coils (inner and outer) and blower is cleaned.
do a close inspection, remove the inner filters and inspect the coil, look at the blower closely, check the other coil for dirt buildup etc.
if these are already clean and passing air with no issue, your problem lies elsewhere.