A friend of mine is going to give me a panzer IV (The turret is almost done) for a good price (I think it's Tamiya ), and I was wondering if it's any good. Also, how could I do this?

Thanks for your time.

All Tamiya PzIV's are good, some are better than others.
The old PzIVD is an ex-motorized kit. There are various holes in the hull that have to be filled and the hull fittings (tools and such) are simplified. The later Pz IV H is somewhat better, but still an ex-motorized kit.
Their PzIV H (early) is a very good kit and Cavalier makes a set of zimmerit for it.
Their newest PzIV J is also very good.
Of course there is PE available for all
I think that is all of the Tamiya PzIV's but I am not sure. I am working from memory, and when I do that I have been accused of using faulty equipment.......LOL

I've done numerous Tamiya PzKpfwIV's and I never had any complaints. The cast on detail is fine so you dont need to go crazy trying to attach teeny little detail pieces. From the basic kit, you can really make an exceptional model, and the sky is the limit with after market additions. To build the bridgelayer? I would suggest you get as many photo's of this as you can and then do the best you can to determine the measurement of the bridging equipment. You may have to only go by what seems to be right proportionaly unless you can develop a scale to use in relation to your photo. This shouldn't be too hard to do since the PzKpfw IV hull was 591cm (232.7 inches) long. (data from Ausf. D over all length - some versions are listed as longer, but I believe it must include gun tube because the difference in length is too great to be typical hull changes) The width with out skirts is 286cm (112.6 inches).

Once you determine the size of the bridging equipment and how it mounts to the vehicle to the best of my knowledge you will need to fabricate the components from styrene. I think maybe the best place to start on this woud be to be on the side panels in order to get the correct profile. From there I would look into the structure and internal bracing. Then I would look into how to most effectively make the deck. Then I would look at getting it on the hull.

I think it will be a little time consuming but the results will be stunning. Good luck.