If it were me I would refresh myself with the OW/AOW syllabus stuff such as dive decompression theory, tables and so on, you might be surprised how much you have forgotten, and then I would try to get a one on one with a DM/Instructor in confined water.
I would ask the LDS basically to do a scuba review/refresher type dive - focussing on a weight and buoyancy check, refresher on mask clearing, regulator recovery and ascent and descent procedures. See how quickly it all comes back, you might be pleasantly surprised and find that is all you need.
However this should show you what else you might need, which you can then sort out with the LDS.
Your profile says you own your own gear - don't forget that if it has sat un-used for four years you should really as a minimum get the regulators and BCD checked and serviced to make sure they have safely survived storage in a fit state to trust your life to them again,
Grab the chance - get wet again and enjoy - have fun - Phil