What equipment would one use to modify a virus?
I'm no expert at this and I would welcome any changes to this post. First you need to decide, what your target organism which you want to infect is (e.g. mammalian cells, bacterial cells) and based on that you choose your viral vector as listed in this article. Generally for mammalian cell stable transfection (usually you want the genetic materials you introduced to persist between cell divisions hence stable transfection) and transformation (just a general statement about changing cells as you have introduced, usually foreign genetic material but transformation is not necessarily the same as making something immortalised, which means the cells won't stop dividing i.e. becoming cell lines or in lay term cancerous) scientists tend to use lentiviruses, which are retroviruses, similar to HIV and they can even infect non dividing cells (so this should allow your imagination to run wild!). Once you have decided what the best viral vehicle for targeting your cells of interest is then you essentially transfect the plasmid DNA (packaging vector), which produces the virus protein package, into cells, whose job becomes to produce the virus as those cells have the required cellular machinery for this purpose. These cells are often 293T packaging cells. Along with the plasmid (circular) DNA, which produces the virus package, you co-transfect the packaging (e.g. 293T) cells with another plasmid, called lenti-vector, which does whatever you want it do, such as express a particular protein or microRNA or whatever but the idea is that stuff produces by the lenti-vector should not be toxic to the target cell (i.e. the cells you intend to target), unless thats what you want it to do.

Now as you can see, you can play around with two things here, first the packaging vector, to change the behaviour of the virus if you wish. And second the lenti-virus vector, to produce whatever you want it to! Once the packaging cells made your viruses, containing your lenti-vector, the virus get secreted into the media, which the packaging cells are in so you have to extract the media, congaing the virus, and concentrate the virus using centrifugation. Once you got the virus then you can use it to transform the (target) cells you wish. 

For the lab based procedure of how you make the virus and what equipments you use and how to concentrate the virus then please see this link, although its a little technical. In this case, the packaging vector is fuGENE 6 and the lenti-vector or just plasmids of interests are listed (please not that I do not endorse any products mentioned here and I'm just using it as an example).

Now for making the packaging plasmid (making the virus), you often use the genetic materials from a virus and change it through a procedure called polymerase chain reaction (PCR). Same goes for the lenti-vector/plasmid as they are derived from somewhere and then change through time using PCR and restriction digests, which is an equivalent of genetic material cut and paste, to make the vectors and products of interest. Once all is done the the virus can infect the target cells and effect it based on its designed function (defined by the two vectors I described).

If the above response does not answer you question, since it is currently very broad, please make further clarification to the question so that I can modify my response accordingly.