Hi.
Wt loss and perindopril will be important. The perindopril not only lowers the BP but also minimises protein leak from the kidney (i.e reduces proteinuria) which is all for the good.
The biopsy is just under local, and maybe some sedation. A fine needle is used to take a core of tissue from the kidney, which can be quite deep in, but the kidney itself isn't that sensitive (pain wise) compared to skin, so once the local is in it may not be too bad. The main thing will be your physician will explain what to expect each step of the way. Some rest will be advised after the biopsy to minimise bruising (haematoma) around the kidney. There may be some visible blood in the urine afterwards, and this almost always settles spontaneously. Serious bleeding or major kidney damage is quite rare.