Claiming from a guarantor

In an arguement with his partner, a tenant kicked in the front door and also the bedroom door. neither were repairable and, when he appeared in court, he was ordered to pay me £700 compensation. I'm told that £5 will be deducted from his benefits each week and this sum will be shared between myself and another person. The debt will take almost 6 years to pay off. The advice I've been given is that I should go to the guarantor for payment, but a couple of questions arise:
1. The female is still in residence, but I know she plans to move. If she decides to ask the council to stop the direct rent payments, she'll have the deposit she needs to move on and I anticipate she'll let us know she's left, after she's gone and there may be rent arrears. So,should I wait until she's gone before claiming from the guarantor, so that I can include any rent arrears and cleaning (the shed will need fumigating after the tenant kept a dog in there) etc., or should I claim for the damage now and then make another claim when any arrears and other costs are known.
2. How would I go abot making a claim from the guarantor, either now or after the tenant has left? Is it just a letter, outlining the costs I'm claiming for, or is there a more formal procedure/template etc that I would be better off using. Needless to say, I'll ensure I register the delivery.

Thanks