So sorry to hear of your relatives plight.
If you are a main beneficiary of this new will and not the old one then you should not be involved in drawing up or witnessing the will.
If the new will is a variation of the old will then do you have a copy of the old will to use as a template.
If your relative is in a lot of medical distress with pain and other meds is there a risk their mind might not be as sharp as possible? Then they may not be in a position to fully sign the will.
At the least, the will should state their full name and address. That this is their last will and supersedes previous ones
Appoint an executor
Say what bank account all debts should be paid from
List out all assets and who is the beneficiary of each of them.
Try not to forget any asset, house, car, contents. Bank accounts, car, pensions etc..
Make sure to give the residue of the estate to someone.
Make sure to get someone to read it out to your relative so they can sign it and get two non relatives to sign, and date it, and be sure to capture all their contact details, & even their job title and employer.
If there is more than one page get your relative to sign and date all pages and number the pages. 1 of 2, two of two, etc.
if there are minor children then list their care needs, guardians etc separately on the will.
Try not to be clever with the legal talk unless you are just making variations of a previous will of your relative, just be as plain and clear as possible.
The hospital may not agree to letting any staff witness a will, and may actively deter relatives pushing for changes in a will.
If your relative just wants to change one think from the previous will, perhaps just make a codicil to the will, and say clearly say what is out of the last will and what replaces it.
IANAL so progress with caution.